When the mosquito now infamous for spreading the Zika virus suddenly showed up thousands of miles from anywhere it would usually call home, a California insect abatement officer was confounded.
Steve Mulligan and his equally puzzled colleagues first encountered the Aedes aegypti mosquito in 2013, in their work for the Consolidated Mosquito Abatement District in California's Central Valley. Until then, no one had ever reported seeing the mosquito in the area.
Most puzzling to Mulligan, the agency's manager: why had the mosquito popped up around Fresno?
"It was way out of its range," he said.
As Mulligan searched for an explanation, he kept coming back to the warmer temperatures blanketing the state's prime agricultural region year after year.
"We started to realize climate change was probably a part of the reason why we were seeing this mosquito," he said.
As world health officials scramble to combat the spreading virus, which could infect as many as 4 million people this year, scientists and public health officials see the outbreak as an omen in a world steadily warming under the effects of climate change.
"[Zika] is the virus of the moment but can be taken as an indicator of a future where changes in temperature provide a more hospitable environment for viruses to replicate and be transmitted," said Colin Parrish, a professor of virology at Cornell University.
The World Health Organization has designated the Zika virus a global public health emergency, assigning it the highest level of urgency.
The most alarming outbreak of the Zika virus erupted in Brazil in May, and has since spread to 25 countries and territories in Latin America and the Caribbean.
In the United States, at least 48 cases of Zika have been reported in nearly a dozen states, including Florida, where a health emergency has been declared in four counties. The infections in the U.S. have been reported in people sickened while traveling outside of the country. (The CDC has confirmed one case of the virus being transmitted sexually in Texas.)
Although the virus generally causes mild to moderate symptoms in infected adults, it is generating worry over its possible link to microcephaly, a condition that causes babies to be born with unusually small heads and often with brain damage.