Climate change raises the risk of Zika and other diseases, scientists say

Aedes aegypti mosquitoes float in a mosquito cage at a laboratory in Cucuta, Colombia, Thursday, Feb. 11, 2016. The laboratory, run by the Health Institute of Norte de Santander, the Colombian state that's been hardest hit by the Zika virus, keeps samples of mosquitoes collected from different areas to study their resistance to insecticide and adjust the formula for fumigation campaigns. (AP Photo/Ricardo Mazalan)

In just over a year, the infamous Zika virus spread to over 30 countries in South America with an estimated 1.5 million people infected in Brazil alone and scientists predict that the risks will get worse with climate change. 

The Zika outbreak has been linked to microcephaly, a deformation in newly born babies, and Guillain-Barré syndrome, an autoimmune disorder that could cause paralysis, according to the World Health Organization. The spread of the virus poses significant threats to human health.

“Climate change poses a risk to the spread of vector-borne diseases like Zika, which transmits through mosquito vectors,” said Paulo Verardi, an assistant professor of pathobiology at the University of Connecticut, who is developing a vaccine for the virus.

“We were really thinking about the effects of climate change early on, and not just on rising sea levels, but on mosquitos,” Verardi said. “When the climate changes, the distribution of mosquitos changes. What that means is that certain mosquitos that are constrained to the tropics now are essentially expanding.”

Over 60 percent of the U.S. population live in areas vulnerable to the seasonal transmission of Zika as mosquitos spread to favorable environments, according to a press release by the European Climate Foundation. 

The threat for Connecticut at this point is limited, but there are certain elements about this particular Zika outbreak that are novel, including how explosive the spread has been.
— Paulo Verardi, an assistant professor of pathobiology at the University of Connecticut, who is developing a vaccine for the Zika virus.

Verardi went to Brazil last summer, where the outbreak was most severe, and experienced temperatures in the 70s and 80s, he said. Since it was winter there, temperatures were expected to be in the 40s and 50s.

“It turned out to be the warmest July on record for that part of the world,” he said, adding that the conditions were ideal for mosquito outbreaks.  

Although the Zika-carrying mosquito is not found in the northeast U.S., changing environmental conditions pose a risk. 

“We are on the borderline,” Theodore Andreadis, director of the Connecticut Agricultural Experiment Station, said. “With mild winters and hotter summers we do suspect that the mosquito may make further in-roads in the state [Connecticut].”

The greatest risk comes from people who travel from South America to the U.S., Andreadis said. If travelers introduce the Zika-carrying mosquito to places where environmental conditions are just right, it could proliferate and infect people.

“There’s another species of mosquito too,” Andreadis said, referring to a species that is found in Connecticut called the Asian tiger mosquito. “It has been shown to be a competent vector and could transmit the virus if it picks it up.”

Despite the risks, both Andreadis and Verardi said they are not concerned about Zika in Connecticut because of the state’s mosquito control measures.

“The threat for Connecticut at this point is limited, but there are certain elements about this particular Zika outbreak that are novel, including how explosive the spread has been,” Verardi said. “This virus was not considered a threat at all. There have been two outbreaks in the past and it didn’t seem like it caused microcephaly.”

While scientists still don’t fully understand the Zika virus, Steven Szczepanek, an assistant professor in pathobiology at UConn, said climate change would affect the spread of many other viruses. Szczepanek teaches a course on emerging infectious diseases, which includes a section on the effects of climate change.

“Most emerging infectious diseases, something to the effect of 80 percent, are zoonotic, meaning that they are transmitted from animals to people,” Szczepanek said. “Climate change not only affects the zones in which we can find new mosquito and tick vectors, it also changes where different species of animals live.”

This could affect where and how much of the virus gets into the environment, he said, warning that Lyme disease could become more of a problem in Connecticut as tick populations grow because of an increase in average temperatures.

With changing climates, scientists expect a wide range of abnormal natural patterns, including those of wildlife and environments, but predicting their effects is complicated, Verardi said.

More rain, for example, could wash away the sewage where mosquitos breed, but could also leave behind large pools of stagnant water, which are also favorable to mosquito reproduction. Verardi said that scientists are often convinced of one result, but observe the opposite.

“Zika is so new, so we don’t know what’s going to happen,” Verardi said. “The reality is that a lot of this is unknown.”


Diler Haji is a campus correspondent for The Daily Campus. He can be reached via email at diler.haji@uconn.edu.