Almost all of Brazil’s latest wave of malaria cases have the Amazonian region as their backdrop, with Acre, Amazonas and Pará registering the highest numbers. Pará’s state health secretariat has launched an emergency plan in the hopes of tackling high disease rates, which includes encouraging residents to use repellent-laced nets in their homes, and will increase resources for lab testing and professional training.

While the Ministry of Health blamed “environmental conditions” and the “diseases own cycles” for the recent malaria outbreaks, scientific experts interviewed by The Brazilian Report believe that the reasons behind the outbreaks of malaria, Zika, dengue, and Chikungunya are more complex.

Environmental changes

Without previous exposure, people are more susceptible to disease – something which Dr. Margareth Capurro, a University of São Paulo researcher, says applies to mosquito-borne diseases as well. According to Capurro, this partially explains why the Zika virus hit Brazil so hard in 2015.

“No-one is protected, because no-one had ever had contact with Zika,” she said. “So everyone who ended up coming into contact with the virus ended up developing the illness.”

Capurro says that high rates of disease contraction are usually followed by relatively low rates the following year, owing to their exposure during an outbreak. “It’s like the people have already had contact with the virus have been vaccinated.”

Environmental factors also play a role, according to Dr. Max Jacobo Moreno-Madriñán, a public health specialist who investigates the relationship between the environment and vector-transmitted diseases. In his research, he has found that factors like temperature, rainfall, vegetation, land cover and land use – all factors measurable by satellite technology – can be used to predict mosquito presence and potential disease outbreaks.

“El Niño is very determinant,” he says. But for Dr. Moreno-Madriñán, diseases like malaria and Zika are ostensibly far more linked to social and economic circumstances than the climate. “Socioeconomic conditions and standards of living seem to be even more of a determinant than physical aspects.”

Socioeconomic factors act as catalysts

Dr, Moreno-Madriñán is one of many to conclude that cultural practices, as well as social and economic practicalities, underpin outbreaks of mosquito-borne diseases. As new-borns with microcephaly were linked to Brazil’s Zika virus outbreak in 2016, some began to panic: the same environmental conditions that permitted the Aedes Aegypti mosquito to flourish in Brazil were also present in parts of the southern US.

But outbreaks, expected in U.S. states like Florida, never came. Generally higher standards of living meant that, despite having similar climatic conditions, U.S. residents were largely protected from arboviruses. In Brazil, however, living conditions could be the catalyst for recent outbreaks.

“We’re seeing a confluence of factors: we’re seeing poverty combined with urbanization, combined with human migrations, combined with climate change,” Dr. Peter Hotez, Dean of the Baylor School of Tropical Medicine, explained to The Brazilian Report. “All of those things are creating what I sometimes call the perfect storm, that’s allowing these arboviruses to flourish.”

Dr. Hotez expects that disease outbreaks will get worse in the near future, and will lead to rising death tolls in developing countries. Dr. Paolo Zanotto, a researcher at the University of São Paulo and one of the leaders of the Zika Network, believes that disease outbreaks will also worsen across the globe.

“The factors that are causing the problem are not actually diminishing, like overpopulation, ecological devastation … these things are increasing,” Dr. Zanotto says. “It’s a worldwide phenomenon and is a combination of factors. You have to realize that people are 35 hours away from each other at most, because of airplanes and so on.”

Developing countries will be worst hit

The Aedes Aegypti mosquito. Photo: Alexandre Carvalho

In addition to having climates where mosquitoes are able to thrive, less funding and fewer resources mean that developing countries are likely to be affected more than those in the Northern Hemisphere.

“Climate change disproportionately affects people who live in poverty and in low-quality housing, and they reinforce each other,” Dr. Hotez said. “Things like El Niño and climate change are important factors, but they tend to be revved up when you have the right cascade of social determinants that could also promote disease.”

Higher disease rates may lead to further strains on public healthcare systems and higher death tolls. For many countries, it could also mean a less productive economy, as diseases knock workers back for months on end.

“We’ve been working in low-income communities in Sergipe, where there was a massive outbreak,” explains Dr. Zanotto. “There were a lot of people who couldn’t work for six or eight months because their hands were too bad, they couldn’t move their fingers. This will certainly have an impact on the economy, on social stability.”

But it is unlikely that the economic consequences of mosquito-borne disease outbreaks will be limited to developing countries, thanks to human migration and globalization. “Developed countries should be very concerned by public health in developing countries, because they can still suffer the consequences from imported cases,” warns Dr. Moreno-Madriñán. “It should be a global public health concern.”