yellow fever mosquito

Mosquitoes in America and Asia are more susceptible to being infected with Zika

The Zika virus (ZIKV) was first isolated from a primate in Uganda in 1947, and a few years later its presence in humans was detected in Uganda and Tanzania. Despite its African origin, there have only been sporadic outbreaks on the continent, while in Asia, the Pacific and the Americas there have been major outbreaks since 2007, the worst of which was the 2016 epidemic that spread to more than 60 countries and caused some 5,000 cases of congenital microcephaly among the babies of women who were infected with the virus during pregnancy. Why has Zika caused so much devastation outside of Africa and not on its home continent? A new study offers an explanation to the puzzle.

The difference would be in the mosquito that transmits it. In all cases, it is the yellow fever mosquito, Aedes aegypti, the main vector involved in the transmission of old dengue diseases and yellow fever, but also emerging diseases such as chikungunya or Zika. But within the yellow fever mosquito there are two subspecies. One of them is Aedes aegypti aegypti, with mosquitoes adapted to living in humanized environments, it reproduces in artificial water containers in urban areas and has a preference for biting humans as explained in a previous post. This subspecies originated in West Africa about 5,000 or 10,000 years ago and from there, the slave trade was responsible for introducing it into America and later Asia. The mosquito adapted to urban environments is now widely distributed throughout the world. In contrast, in most of the African continent, there is another subspecies, Aedes aegypti formosus, which inhabits both wooded and urban areas, breeds in holes in trees and does not feel a special attraction to human blood, feeding on a great variety of vertebrates, including people.

Until now, it was believed that this affinity for living close to humans and their blood was the main explanation why Zika had caused more havoc outside Africa than on the continent, but the study provides another piece of information: the related mosquitoes, Aedes aegypti formosus, are less likely to contract and therefore transmit the Zika virus.


The changes suffered during adaptation to human environments were accompanied by a greater ability to become infected

The results suggest that the changes that mosquitoes underwent thousands of years ago when adapting to human environments were accompanied by an intrinsic ability to become infected with this type of virus. To reach this conclusion, the researchers conducted an experiment with mosquitoes from eight populations collected in Africa, America, and Asia. In the laboratory, they were fed blood infected with different strains of the Zika virus to study how they became infected. They observed that the mosquitoes of America and Asia required less viral load in the blood to become infected than the African mosquitoes (Fig. 1).

Fig. 1.  Proportion curves of mosquitoes that become infected with the Zika virus (ZIKV) when feeding on blood at different concentrations of the virus. Each box is the same experiment carried out with different strains of the virus, the colors indicate the origin of the mosquitoes. Source: Mosquito Alert CC-BY based on the original by Aubry et al. 2020. Science 370: 991-996


They designed a second experiment to measure the susceptibility to infection of a larger number of African populations, including those on the west coast that are related to those in America and Asia. Those of the coast of Senegal gave similar results to those of America and Asia, with low doses of the virus in the blood they become infected. They found that in mosquitoes of the Aedes aegypti aegypti subspecies it was easier to find the virus in their salivary glands. Not only are they more susceptible to becoming infected with the virus, but they are more likely to transmit it when they feed on a person and inject their saliva.

All the results establish a strong link between the mosquito domestication process that took place around 10,000 – 5,000 years ago and the transmission capacity of viruses such as Zika. The difference in susceptibility between the two subspecies may contribute to the absence of major outbreaks in Africa, although other factors may exist, including mutations in the virus that have allowed it to specialize and become more infectious in populations outside of Africa.


Aubry F, Dabo S, Manet C, Filipović I, Rose NH, Miot EF, Martynow D, Baidaliuk A, Merkling SH, Dickson LB, Crist AB, Anyango VO, Romero-Vivas C, Vega-Rúa A, Dusfour I, Jiolle D, Paupy C, Mayanja MN, Lutwama JJ, Kohl A, Duong V, Ponlawat A, Sylla M, Akorli J, Otoo S, Lutomiah J, Sang R, Mutebi JP, Cao-Lormeau VM, Jarman RG, Diagne CT. Faye O, Faye O, Sall AA, McBride CS, Montagutelli X, Rašić G, Lambrechts L. 2020. Enhanced Zika virus susceptibility of globally invasive Aedes aegypti populations. Science 370: 991-996

Kotsakiozi P, Evans BR, Gloria-Soria A, Kamgang B, Mayanja M, Lutwama J, Le Goff G, Ayala D, Paupy C, Badolo A, Pinto J, Sousa CA, Troco AD, Powell JR. 2018. Population structure of a vector of human diseases: Aedes aegypti in its ancestral range, Africa. Ecology and Evolution 8: 7835-7848

Rose NH, Sylla M, Badolo A, Lutomiah J, Ayala D, Aribodor OB, Ibn N, Akorli J, Otoo S, Mutebi JP, Kriete AL, Ewing EG, Sang R, Gloria-Soria A, Powell JR, Baker RE, White BJ, Crawford JE, McBride C. 2020. Climate and urbanization drive mosquito preference for humans. Current Biology 30: 3570-3579.e6

Climate and urbanization drive mosquitoes’ preference for humans

The yellow fever mosquito (Aedes aegypti) is known throughout the world for inhabiting urban areas, biting humans and thereby spreading diseases such as dengue, Zika, chikungunya and the yellow fever that gives it its name. The WHO estimates that this species causes 50 million infections and 25,000 deaths a year. Studies carried out in America and Asia found that 95% of the blood consumed by the mosquito is human, demonstrating its preference for us.

However, in Africa, where the mosquito originates from, most of the populations of this mosquito do not have a preference for humans, but for other animals, mainly mammals such as primates and rodents. But this trend could change in the coming years, a new study warns. The increasing urbanization that the continent is experiencing and climate change, will favor the spread of mosquitoes with a preference for humans. And this will increase your ability to spread disease.

The yellow fever mosquito is native to Africa, where most of its populations have no preference for biting humans, unlike their populations in America and Asia

To reach these conclusions, the study authors analyzed the preference of various populations of African Aedes aegypti and the climatic and environmental variables that could explain the differences between them. They collected eggs from 27 locations in sub-Saharan Africa (Fig. 1), which varied in their climatic conditions, ranging from the semi-arid regions of the Sahel, to seasonal forests and rain forests. The other variable they analyzed was the density of the human population present in the area. The mosquitoes were bred in a laboratory where their biting preference was studied, exposing them to human odors and odors from other non-human animals at the same time. In this way they could observe which of them they were heading and calculate the preference of the different populations.

Fig. 1. Location of the populations used in the study. The size of the circle represents the density of human population present in the area. The color the mosquito’s preference for biting humans (reddish) or other animals (bluish). The figure below shows the preference index obtained by giving them a choice between humans or other animals for each of the populations. The point is the mean and the bar is the 95% confidence interval. Source: Mosquito Alert CC-BY from the original by Rose et al. 2020. bioRxiv 939041

Urbanization and climate determine mosquito preference

Most of the populations preferred the smell of the other animals (blue), some did not show preference for one or the other (violets), and only a few of them showed a clear predilection for human smell (red) (Fig. 1) . The taste for human blood was present in those regions with a higher human density. Suggesting that when the human population is large in an area, the most favored mosquitoes are those that tend to feed on people’s blood.

Another factor that explained the distribution of mosquitoes with this preference for human odor was the climate. These mosquitoes are more abundant in dry regions. In them the natural habitats where they usually deposit eggs, tree holes or concavities in the rocks with rainwater, are scarce. Instead, human containers and tanks proliferate to store water. Humans provide mosquitoes with places to breed in environments that are initially unfavorable to them.

Both morphology and genetics show that mosquitoes with a preference for humans, which today have invaded the American and Asian continents, are related to the populations of the Sahel, the region that makes the transition between the Sahara desert to the north, and the savannah to the south. The term of Arab origin literally means “coast”, in reference to the appearance of the vegetation delimiting the sandy sea of ​​the Sahara. The yellow fever mosquito populations that inhabit northern Senegal, in addition to showing a preference for humans, is the one that is genetically related to the mosquitoes that we find today in America and Asia.

The yellow fever mosquito tamed itself

In these semi-arid environments, mosquitoes depend on human habitats to reproduce. Human-made tanks and water drums allow them to inhabit a region where they find few natural habitats to reproduce. Being forced to live together with human populations, where the most abundant prey is humans, natural selection ended up generating mosquito populations with a preference for feeding on humans. Individuals with the mutations in sensory systems that determine their preference for human odors are the most abundant in these populations.

A drier climate and greater urbanization foresees an increase in mosquitoes with a preference for humans in Africa in the coming decades

The combination of dry seasons and dependence on humanized spaces has not only been important in the evolution of the yellow fever mosquito, but has also shaped the evolution of Anopheles mosquitoes that transmit malaria in Africa.

In Africa, the climate and density of human populations are changing, and it is feared that the change in rainfall and the increase in urbanized areas will favor mosquitoes that have adapted to live and feed on humans. That would mean a considerable increase in human populations on the continent exposed to the diseases that this species can transmit.



Crawford JE, Alves JM, Palmer WJ, Day JP, Sylla M, Ramasamy R, Surendran SN, Black WC, Pain A, Jiggins FM. 2017. Population genomics reveals that an anthrophilic population of Aedes aegypti mosquitoes in West Africa recently gave rise to American and Asian populations of this major disease vector. BMC Biology 15: 16

Dao A, Yaro AS, Diallo M, Timbiné S, Huestis DL, Kassogué Y, Traoré AI, Sanogo ZL, Samaké D, Lehmann T. 2014. Signatures of aestivation and migration in Sahelian malaria mosquito populations. Nature 516: 387-390

Kotsakiozi P, Evans BR, Gloria-Soria A, Kamgang B, Mayanja M, Lutwama J, Le Goff G, Ayala D, Paupy C, Badolo A, Pinto J, Sousa CA, Troco AD, Powell JR. 2018. Population structure of a vector of human diseases: Aedes aegypti in its ancestral range, Africa. Ecology and Evolution 8: 7835-7848

McBride CS. 2016. Genes and odors underlying the recent evolution of mosquito preference for humans. Current Biology 26: R41-R46

Rose NH, Sylla M, Badolo A, Lutomiah J, Ayala D, Aribodor OB, Ibn N, Akorli J, Otoo S, Mutebi JP, Kriete AL, Ewing EG, Sang R, Gloria-Soria A, Powell JR, Baker RE, White BJ, Crawford JE, McBride C. 2020. Climate and urbanization drive mosquito preference for humans. bioRxiv:

Takken W, Verhulst NO. 2013. Host preference of blood-feeding mosquitoes. Annual Review of Entomology 58: 433-453


Climate change accelerates the spread of the yellow fever mosquito

The spread of disease-transmitting mosquitoes is primarily a product of globalization, with a long history behind it. The yellow fever mosquito (Aedes aegypti) colonized the American continent from Africa as a stowaway in slave ships that trafficked slaves. With the mosquito came yellow fever to the new continent. Later both would arrive at the most important ports in Europe. The tiger mosquito (Aedes albopictus) has also traveled hidden on commercial ships from Asia to the rest of the world in much more recent times. Globalization has allowed these species originating from tropical regions to invade new areas, but another human phenomenon has also helped: climate change.

The rapid expansion registered by both species in just under half a century has been facilitated by rising temperatures. Climate change has great effects on the distribution of many species by altering the climatic conditions of different regions. Ectothermic (or cold-blooded) organisms, such as mosquitoes, are not capable of generating internal heat, as, for example, we mammals do through various metabolic processes (Fig. 1). This makes your activity dependent on external heat sources. This explains its absence during the cold winter months and its revival in spring. Therefore, a warmer world, like the one we are heading to, is more favorable for tropical species.


Fig. 1. Differences in body temperature with respect to the ambient temperature of an ectotherm, such as the tiger mosquito, and an endotherm, such as the tiger. The temperature of the ectotherms varies with the environmental one, unlike the endotherms that maintain a constant temperature regardless of the ambient temperature. Source: Mosquito Alert (CC-BY-NC-2.0)


In recent years, studies have appeared that predict that both the tiger mosquito and the yellow fever mosquito will have an easier time expanding to areas that are now temperate as average temperatures rise. The warming will allow these species to find new favorable places where they can complete their cycle. Precisely the last study has been based on the ability of Aedes aegypti to complete its cycle in different climatic conditions to estimate how much and where it will be able to expand in the coming years.

A warmer world will favor the expansion of tropical species such as the yellow fever mosquito or the tiger mosquito


Temperature accelerates mosquito development

For this they analyzed how temperature can affect the mosquito in its different stages of development: egg, larva, pupa and adult. The higher the temperature, the faster the transition from one phase to another. For example, from the time a female has fed on blood until she lays her eggs, 8 days pass at 20ºC. But if the temperature is 26ºC the time is reduced to 3 days. Only 2 days if the temperature is 30ºC. Or 4 if it exceeds 35ºC, because the excess temperature also affects them.

Using the temperature values ​​necessary for the animal to survive from one phase to another, as well as its speed as a function of temperature, scientists at Imperial College London and Tel Aviv University have been able to calculate how many times it could complete its life cycle the yellow fever mosquito in every region of the world. A greater number of completed cycles implies more mosquitoes and for a longer time. That directly translates into more likely to transmit diseases such as dengue, Zika or chikungunya.

The more life cycles completed per year in an area, the more mosquitoes and more exposure to the risk of contracting one of the diseases they transmit

Using historical data on world temperatures, as well as future projections under different emission scenarios, they have been able to make a model to predict the efficiency with which the mosquito will reproduce in different places in the coming decades.

In 2030 some regions of the Mediterranean will meet the requirements for the establishment of the yellow fever mosquito

In fact, the mosquito appears to have taken advantage of warming for the past half century. The warming recorded from 1950 to 2000 has allowed the species to expand, both within tropical and subtropical zones, and reaching temperate zones in Asia and America. In 2050 the species will move north more rapidly, especially in China and the United States (Fig. 2). The advance will be between 5 and 6 kilometers a year. It doesn’t seem like much, but it represents a huge annual increase in area and new human populations exposed to the mosquito.

Fig. 2. Predictions of the regions that will meet the climatic requirements in the coming years that may favor the establishment of the yellow fever mosquito. Source: Iwamura et al. 2020. Nature Communications 11: 2130


Europe may also be invaded by the species. The Mediterranean region in a couple of decades will have the ideal climatic conditions so that the mosquito can complete its cycle (Fig. 2). The authors estimate that by 2030 regions of Spain, Portugal, Greece and Turkey will meet the climatic requirements for the species to become established. In fact, in some of these areas it was already present in the past. Athens, for example, suffered a major dengue outbreak between 1927 and 1928, although from the 1950s the species began to disappear from the continent. Precisely for this reason they believe that their models underestimate the mosquito’s colonization capacity, and that if in not too distant times they were able to establish themselves in some regions of the Mediterranean and the Black Sea, with global warming their expansion may be greater than the one predicted by the models.

In 2030 the climatic conditions in southern Spain will be favorable to the establishment of the yellow fever mosquito

These regions where it was present in the past may be on the edge of its niche, so control measures and the climate helped to eradicate it, a situation that will change if the climate does not contribute to its control. Warming implies the globalization of mosquitoes, which in turn implies the globalization of the diseases they transmit.


Iwamura T, Guzman-Holst A, Murray KA. 2020. Accelerating invasion potential of disease vector Aedes aegypti under climate change. Nature Communications 11: 2130

Liu-Helmersson J, Rocköv J, Sewe M, Brännström A. 2015. Climate Change may enable Aedes aegypti infestation in major European cities by 2100. Environmental Research 172: 639-699

Messina JP, Brady OJ, Golding N, Kraemer MUG, Wint GRW, Pigott DM, Shearer FM, Johnson K, Earl L, Marczack LB, Shirude S, Weaver ND, Gilbert M, Velayudhan R, Jones P, Jaenisch T, Scott TW, Reiner RC, Hay S. 2019. The current and future global distribution and population at risk of dengue. Nature Microbiology 4: 1508-1515

Ryan SJ. Carlson CJ, Mordecai EA, Johnson LR. 2019. Global expansion and redistribution of Aedes-borne virus transmission risk with climate change. PLoS Neglected Tropical Diseases 0007213

Wearing HJ, Robert MA, Christofferson RC. 2016. Dengue and Chikungunya: modelling the expansion of mosquito-borne viruses into naïve populations. Parasitology 143: 860-873

Bloodthirsty: the other reason why a mosquito bites

Mosquito females are the only ones that bite, they do it to acquire protein to the development of their eggs. Yes, our blood serves to give rise to a new generation of mosquitoes. But recent work suggests that blood can also act as a snack for mosquitoes in dry and warm periods.

The study, published in Scientific Reports, has found that mosquitoes exposed to dry environments, with a higher level of dehydration, are more aggressive than those that are well hydrated. Dehydrated mosquitoes venture more to land on a host, bite and feed on blood more often than the others. Scientists believe that during periods of drought the risk of disease transmission can increase. More bites more risk of transmission.

The idea that in the dry periods there may be more cases of infection seems contradictory given the great dependence of mosquitoes on water. Most of them lay their eggs in wetlands where the larvae develop. Thus, the number of mosquitoes depends on weather, increasing their number after rains, once there is stagnant water in abundance where they can reproduce. This relationship between climatic conditions and the number of mosquitoes has also been established among diseases transmitted by mosquitoes. One expects that more rain implicates more mosquitoes and more diseases transmitted. But the data don’t always confirm these expectations.

Droughts cause major epidemic episodes of West Nile fever

In the case of West Nile fever, it has been seen that epidemic episodes are greater in the years of drought. The authors believe that their observations may explain why sometimes epidemics occur during periods of drought.

To study how droughts and dehydration alter the physiology and behavior of mosquitoes, they designed an experiment that they tested on three mosquito species. The species evaluated were: (1) Culex pipiens, the common mosquito that could transmit the West Nile virus in the United States (2) Aedes aegypti or yellow fever mosquito, which can also transmit dengue, chikungunya and fever from Zika, and (3) Anopheles quadrimaculatus, a mosquito from the North American Atlantic coast capable of transmitting malaria.

Mosquito Alert

Fig. 1. Mosquitoes were offered an artificial host made with a collagen membrane, which contained chicken blood to study the biting rate at different levels of dehidration. Figure based on the original: Hagan et al. (2018) Scientific Reports 8: 6804. Source: Mosquit Alert (CC-BY-NC-2.0)


The researchers exposed hundreds of mosquitoes of each species to different temperature and humidity conditions to generate individuals with different levels of dehydration. In the experiment they included another factor, as some mosquitoes had access to water or nectar with which to hydrate while others had no access to any type of liquid. After some time in these conditions, its effect on the mosquito behavior was analyzed. For this, the mosquitoes were offered an artificial host made with a collagen membrane at a temperature of 37 °C, covered with artificial sweat to attract mosquitoes, which contained chicken blood (Fig. 1).


Thirsty mosquitoes’ bite more

When quantifying the times, they landed on the artificial host and fed on it; they saw that the number of bites was higher among dehydrated mosquitoes that also had no access to water or nectar. Only 10 percent of the mosquitoes with access to water landed and bite the host, while among the mosquitoes deprived of water was 30 percent. Mosquitoes in conditions that recreated a drought bite much more than the other mosquitoes (Fig. 2).

The sensors available to mosquitoes to detect a host, make it easier for them to detect a host than to locate a water point with which to hydrate when they are thirsty. The highest rates of West Nile virus transmission observed during droughts could be due to mosquitoes using blood to replace the water they lose.

Mosquito Alert

Fig. 2. Mosquitoes in condition that recreated a drough with higher levels fo dehidration bite much more than well hidrated mosquitoes. Figure based on the original: Hagan et al. (2018) Scientific Reports 8: 6804. Source: Mosquit Alert (CC-BY-NC-2.0)


Knowing the climatic conditions that alter mosquito bite behavior has practical applications as it can be incorporated into epidemiological mathematical models. The abundance of mosquitoes is an important factor to consider in these models, but studies like that one show that environmental factors alter mosquito-human interaction so that the risk of transmission can vary with weather.

The increase in bites to quench thirst is not the only mechanism that can explain the relationship between drought periods and epidemics. Other studies have found that during droughts there are fewer wetlands and resources, which helps animals and mosquitoes come into contact more easily, favoring disease transmission. In addition, in the few existing wetlands there is a greater concentration of nutrients necessary for larval development. In these temporary and ephemeral ponds the proliferation of mosquitoes is favored by the absence of large predators, which inhabit permanent aquatic environments. The periods of heat and drought not only affect predators of aquatic environments but also the potential predators of adult mosquitoes, allowing their populations to be larger.

In short, that periods of drought can favor the proliferation of some species of mosquitoes, and make that mosquitoes become more aggressive. The increase in temperatures caused by global warming could lead to more frequent and longer periods of drought in areas where mosquitoes are a threat to human health.



Barnard DR, Dickerson CZ, Murugan K, Xue RD, Kline DL, Bernier UR. 2014. Measurement of landing mosquito density on humans. Acta Tropica 136: 58-67

Chase JM, Knight TM. 2003. Drought-induced mosquito outbreaks in wetlands. Ecology Letters 6: 1017-1024

Hagan RW, Didion EM, Rosselot AE, Holmes CJ, Siler SC, Rosenlade AJ, Herdershot JM, Elliot KSB, Jennings EC, Nine GA, Perez PL, Rizlallah AE, Watanabe M, Romick.Rosendale LE, Xiao Y, Rasgon JL, Benoit JB. 2018. Dehydration prompts increased activity and blood feeding by mosquitoes. Scientific Reports 8: 6804

Paull SH, Horton DE, Ashfaq M, Rastogi D, Kramer LD, Diffenbaugh NS, Kilpatrick AM. 2017. Drought and immunity determine the intensity of West Nile virus epidemics and climate change impacts. Proceedings of the Royal Society B 284: 20162078

Paz S. 2015. Climate Change impacts on West Nile virus transmission in a global context. Philosophical Transactions Royal Society B 370: 20130561

Paz S, Malkinson D, Green MS, Tsioni G, Papa A, Danis K, Sirbu A, Ceianu C, Katalin K, Ferenczi E, Zeller H, Semenza JC. 2013. Permissive summer temperatures of the 2010 European West Nile fever upsurge. PLoS One 8: e56398

Romano D, Stefanini C, Canale A, Benelli G. 2018. Artificial blood feeders for mosquitoes and ticks – where from, where to? Acta Tropica 183: 43-56

Shaman J, Day JF, Stieglitz M. 2005. Drought-induced amplification and epidemic transmission of West Nile virus in southern Florida. Journal of Medical Entomology 42: 134-141

Wang G, Minnis RB, Belant JL, Wax CL. 2010. Dry weather introduces outbreaks of human West Nile virus infection. BMC Infectious Diseases 10: 38


Vall d’ Hebrón leads the development of an early warning system for the emergence of autochthonous arboviruses including Zika and dengue fever

  • The Infectious Diseases Service of Vall d’Hebron is coordinating the development of risk alert system for the emergence of autochthonous arboviruses in Catalonia including Zika, dengue and chikungunya within the framework of a PERIS (Strategic Plan for Health Research and Innovation) research project. 
  • This warning system or prediction engine is the final product resulting from the Integrated Platform for the Control of Arboviruses in Catalonia (PICAT), coordinated by Vall d’Hebron, and which integrates information from different organizations involved in the control of these diseases.
  • It is estimated that the prediction tool will become operative in summer 2019


El Dr. Israel Molina lidera el PICAT.

Dr. Israel Molina leads PICAT.


Within the framework of a PERIS research project, the Infectious Diseases Service of Vall d’Hebron Hospital in Barcelona is leading the creation of a information technology-based alert platform to assess the risk of the emergence of native arbovirusesin Catalonia. Currently, these diseases are imported: in other words, residents of Catalonia affected by the dieseases are always infected in other countries. However, there is a risk of infection in Catalonia through an arthropod vector, e.g. the common mosquito or the tiger mosquito, since they can bite a person who is in a period of arbovirus transmissibility and transmit it to another person. It is important to consider that arboviruses represent an important risk to public health, such as is the case for Zika, dengue, chikungunya or the the West Nile virus, particularly in vulnerable populations such as pregnant women and people with low immunity. The growing presence of the tiger mosquito in the Mediterranean makes it the main threat for the establishment of native arboviruses in Catalonia.

This alert and prediction engine system will be the final tool emerging from the Integrative Platform for the Control of Arboviruses in Catalonia (PICAT). The platform is composed of different organizations that provide information related to arboviruses and the risk that they may become native. In this sense, the goal is to carry out careful monitoring of the presence and evolution of these pathogens in Catalonia. Vall d’Hebron’s Program for International Health of the Catalan Institute for Health (PROSICS) leads PICAT with the collaboration of the Catalan Agency for Public Health (ASPCAT), the Barcelona Public Health Agency (ASPB), the Agency for Public Health of the Diputación de Girona (Dipsalut), the University Institute for Research in Primary care (IDIAPJGol), the Centre for Ecological Research and Forestry Applications (CREAF), the Blanes Center for Advanced Studies (CSIC-CEAB) and the Catalan Institution for Research and Advanced Studies (ICREA), along with the support of Obra Social “la Caixa”, citizen science project Mosquito Alert; the Barcelona Institute for Global Health (ISGlobal), and the Consortium for Environmental Policies in the Ebro Region (COP), the Roses Bay and Baix Ter Mosquito Control Service, and The Baix Llobregat County Council Mosquito Control Service.

Most of these organizations make up the Inter-institutional Commission for the Prevention and Control of Mosquito vectors in Catalunya, the umbrella organization responsible for the surveillance and control of arboviruses in Catalonia. It was within the framework of this Commission that the Protocol for Surveillance and Control of Arboviruses Transmitted by Mosquitos in Catalonia was drafted, implemented in 2015 and coordinated by ASPCAT.

Today, “the risk that arboviruses become autochthonous is low” explains Dr. Israel Molina, coordinator of the Unit for Tropical Medicine and International Health from the Infectious Diseases Service of Vall d’Hebron,  “but this risk is increasing due to the growing presence of the Tiger mosquito and cases of imported arbovirus from the large volume of travellers between Catalonia and the endemic areas.”

A real-time warning system which will alert the risk of autochthonous arboviruses

As explained by Dr. Israel Molina, “with PICAT we want to go beyond a simple, static prognostic of arboviruses in Catalunya. We want to be ahead of the game and detect, in real time, the risk that they will become native.” To achieve this it is essential to develop an early warning system that is fed information by the various agencies involved in the control of these diseases and which will learn how to detect the mentioned risk.

Equip PICAT.

Equip PICAT.


The information that currently feeds PICAT are data relating to cases of arbovirus or suspected disease, climate data, and information on the presence of tiger mosquitos in specific areas. The information on the presence of the tiger mosquito comes from the different mosquito control services and the alerts made by citizens using the Mosquito Alert app. Future alert system will be based on the infrastructure of the map of citizen alerts from the Mosquito Alert citizen science project, and the notifications, confirmations and entomological study of the alerts made in Catalonia from the established actions in the protocol for tiger mosqutio for vigilance and control. By way of citizens using the Mosquito Alert app, the Mosquito Alert project collects photographs of tiger mosquitoes, yellow fever mosquitoes and their breeding places in real time.

Therefore, the warning system that is being developed will be based on software that will allow all this information to be combined and will function as an algorithm to evaluate the risk of autochthonous arboviruses. “If, for example, in a specific area, primary care physicians warn of an increase in cases of dengue, citizens alert about an increased presence of the tiger mosquito, and mosquito control services corroborate this presence and point out that rains are expected that can favor the proliferation of mosquitoes, the alarm will be triggered since the right conditions are being produced with the increased possibility that the mosquitoes may bite infected people and native dengue can appear. Therefore, we will act before this occurs”, adds Dr. Israel Molina, who is also a researcher at the Infectious Diseases Group of Vall d’Hebrón Research Institute (VHIR).”

The algorithm, therefore, will be an intelligent alert system that will learn with new data and experience to be more and more reliable, effective, and quick to assess the risk of emergence of indigenous arboviruses. This system is intended to lend information technology-assisted risk alert to public health maneuvers already carried out in the framework of the Protocol for the Prevention and Control of the Arboviruses Transmitted by Mosquitoes in Catalonia.

Available the Mosquito Alert annual report 2016

The document brings together the results of all the activities carried out by the project during 2016 on citizen participation, scientific activity, expert validation, maps, data, education and internationalisation among other innovations.

First, the project has incorporated the yellow fever mosquito as another target species, in addition to the well-known tiger mosquito. We have worked on a new map of observations that will allow to expand the activities of surveillance and control of the tiger mosquito and the yellow fever mosquito by the responsible entities. We have also improved the Mosquito Alert app and every time we receive more and better tiger mosquito observations. Finally, this 2016 has also been important to take the first steps towards the internationalisation of the project and we have been released in the educational field.

Mosquito Alert, recognized by the United Nations

The project has been included in the portal of the Environmental Programme of the United Nations (UNEP) as an exemplary citizen science project promoting human health worldwide.

Los datos de Mosquito Alert se pueden consultar en el apartado de Salud Global del portal UNEP.

El mapa de Mosquito Alert se puede consultar en el apartado de Salud Global del portal UNEP.

As of November 2016, the map and data of citizen observations created through Mosquito Alert have been accessible through the international portal of the United Nations Environmental Programme (UNEP). The UNEP selects some of the foremost projects related to health and the environment, and considers Mosquito Alert as a benchmark project tackling world health issues. “The philosophy of our project is valued, based on involving citizens in public health issues on a worldwide scale through citizen science,” says Frederic Bartumeus, director of Mosquito Alert and researcher at ICREA, CREAF, and CEAB-CSIC.

The project became known to Members of the European Parliament when John Palmer, Mosquito Alert member and researcher at Pompeu Fabra University (UPF), presented the project in Brussels in September 2016. “It was at that point that the Director of Research at UNEP Jacqueline McGlade became interested in highlighting Mosquito Alert within this international portal,” says John Palmer.

Greater visibility within Europe

Some of the UNEP’s objectives are to help set the European environmental agenda, promote greater visibility for some of the most troublesome environmental and health issues, and provide solutions to such problems. It also serves as a reference portal for information on health and the environment. “We are put on the same stage as large initiatives such as the Noah project on biodiversity. Forming a part of this portal provides us with new opportunities and will position the project on the European level and internationally,” says Bartumeus.

Hong Kong prepares to use the Mosquito Alert app

A multidisciplinary team of citizen scientists, civic hackers, medical students, and “big data” experts from Hong Kong have started working to adapt the Mosquito Alert citizen science project to their region. The initiative began after the group participated in an international Hackathon addressing the worldwide status of the Zika virus where they learned about the Mosquito Alert project.

Equipo de Hong Kong.

The Hong Kong team.

Beginning a few months ago, a team of open science enthusiasts and experts on data management and mobile device application development have started working on the Chinese version of the Mosquito Alert app. Their objective is to fight against mosquitos transmitting diseases in Asian countries. “We want to adapt the app to our area in order to deal with the mosquito problem that we have in Hong Kong,” says Scott Edmunds, from Open Data Hong Kong and executive editor of GigaScience in Hong Kong. In this region, mosquitos and particularly the tiger mosquito are spreading, and abundant for much of the year. “Our objective,” says Abbie Jung, co-founder of Synergy Social Ventures, “is to be able to mark on a map the places where the mosquitos breed, and not only the tiger mosquitos of which there are many, but also the yellow fever mosquito which is found in Taiwan and on the island of Hainan.”

The Chinese version of the Mosquito Alert app will allow citizens to send photos of adult mosquitos and their breeding sites, all of which will be geo-located on a map. And, just like the Spanish version, photos sent with the app will be validated by a team of entomologists. So, while much of the app will stay the same, “it is possible that in the long term we will make some changes to the app, but that will have to be seen in time,” says Mendel Wong, information technology expert. For the time being the application has already been translated to traditional Chinese for Hong Kong and Taiwan, and work is underway to translate it to simplified Chinese making it more accessible to the billion Mandarin speakers in mainland China. The translation work has been carried out by Sabrina Wong, a medical student studying in the University of Hong Kong interested in human rights and public health issues.

Versión 'demo' china de la app Mosquito Alert.

‘Demo’ version of the Mosquito Alert app in Chinese.


Yellow fever alert

On top of grave worries about Zika, public health officials in China are also very concerned about yellow fever, and in April alone there were 11 reported cases of yellow fever imported from Angola. There hasn’t yet been any case of local transmission, but the record spring rains this year could favour vector breeding, thereby increasing the risk of an epidemic. According to the Hong Kong team, “we need to concentrate our attention here since we already have problems with stagnant water in urban areas, such is the case with the Pearl River.”

The road to open data

As an additional benefit of this collaboration, the Hong Kong team hopes to contribute in many more ways to the project, such as helping transition Mosquito Alert towards open data. According to Scott Edmunds, “it would be a big step forward to standardize the documentation of data generated by this platform.” The philosophy of open data is becoming more and more common among projects working with data, and consists in making them more accessible and available to everyone.

3 steps to start with Mosquito Alert

With the Mosquito Alert app you can send observations of tiger mosquitoes or yellow fever mosquitoes, including GPS location and the photographs. You can also do this if you see public places with mosquito larvae, especially storm drain, or other public places which could be possible breeding sites of these two species. This information is useful for scientists to study how these mosquitoes are distributed geographically. In addition, governments and environmental and public health managers can make use of the data and learn where there are problems in order to act.

1) Find tiger mosquitos or yellow fever mosquitos

They are small and dark with white stripes. The tiger mosquito has 1 single white stripe on the head and yellow fever has several white stripes in the form of a lyre. We will help you to identify them!

Credits: J. Luis Ordóñez CC BY NC 2.0

2) Discover breeding sites

They hide in containers or small spaces with stagnant water. We seek reports of breeding sites in public places, especially storm drainsRead more details here.

3) Send your observations

Photographing mosquitoes: to catch a mosquito, try to trap it in a pot or cup. Then, if you can, hold it by the legs, zoom in and try to make the stripes of the head and chest visible. You can also add pictures from other angles.

Reporting breeding sites: add a picture of the breeding site itself and one of the general area. Also, if you can, add another photo showing water or larvae inside the breeding site if this can be seen.

Discover other tips!

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Mosquito Alert coordinators