A team of researchers from Brazil and Argentina propose several ideas for the many mosquito-borne disease outbreaks in a paper recently published in the Journal of Medical Entomology.
In the article, the authors point to four main factors influencing the spread of mosquito-borne viruses.
- A diverse mosquito and host fauna. According to mosquitocatalog.org, 862 mosquito species can be found in South America, 462 in continental Central America, and 192 in North America. Furthermore, the continents host thousands of species of birds and mammals, the primary hosts for mosquito-borne viruses. While not all of the mosquito species are vectors of diseases, such a large population offers the viruses ample opportunity to adapt to new vectors and infect new hosts.
- Global warming. Mosquitoes require external heat sources to regulate their temperature, so they are very dependent on climate to function. While the ecology of viruses and their vectors is complex, a warming climate could be one factor aiding vectors’ range expansion.
- Increased international travel. Mosquitoes and viruses have taken advantage of global travel for centuries. For example, the slave trade may have introduced yellow fever and dengue to the Americas. Later, the Asian tiger mosquito, Aedes albopictus, which is a vector of multiple viruses, arrived in the U.S. in ships returning from the Pacific theater of World War II. More recently, Zika is believed to have arrived in Brazil through an international canoeing competition or the soccer World Cup.
- Urbanization. In the past 50 years, the world’s population has grown by more than four billion people, and now more than half of those people live in urban areas. However, inadequate infrastructure in urban areas in developing or underdeveloped countries can create prime breeding sites for mosquitoes (such as in rainwater collection containers in areas without a reliable water supply) and increase human contact with mosquitoes (such as in houses without air conditioning and with screenless windows).