Brazil finds Zika in common household mosquitoes

Researchers in Brazil have found Zika in Culex mosquitos—a variety of the blood-sucking insect 20 times more common than the ones previously known to carry the virus.

Thursday’s findings are inconclusive and researchers cautioned they have yet to determine if Culex can transmit the virus to humans.

But the discovery is a blow to Brazilian health officials as they scramble to get the spread of Zika under control before thousands of visitors arrive for the summer Olympics, which starts in two weeks.

So far, Zika’s primary carrier has been Aedes aegypti, a far less common strain of mosquito. Up to this point, most researchers have studied Aedes mosquitoes to develop Zika counter-measures.

But on Thursday, scientists at the Oswaldo Cruz Foundation, a public institution attached to the Brazilian Ministry of Health, collected 500 Culex specimens and found Zika in three pools—about 30-45 mosquitoes. The presence of the virus does not guarantee the mosquitoes can transmit to humans, but researchers are still troubled.

“It’s very bad news for Brazil,” said Constancia Ayres, the entomologist who conducted the research, according to The Globe and Mail. “We have a national program for controlling Aedes—but we have nothing for Culex—so if Culex is an important vector then we have to start from zero.”

Culex mosquitoes have many different characteristics than Aedes. Culex bite during the night, while Aedes bite in daylight. And Aedes breed in clean water, but Culex thrive in polluted channels—particularly concerning since many cities in Brazil have had sewage system problems for years.

But other health officials are slow to panic.

“The study would need to be replicated to have a better understanding of possible implications,” said Tom Skinner, a spokesman for the U.S. Centers for Disease Control and Prevention (CDC), according to CNN. “[A] body of scientific evidence to date clearly points to Aedes being the primary vector implicated in Zika outbreaks.”

Since the World Health Organization labeled Zika a global health crisis earlier this year, the virus has continued to plague Latin American countries but has yet to reach crisis levels in the continental United States.

And while the amount of Zika cases in Brazil has declined in recent months, that hasn’t stopped dozens of Olympic athletes from skipping the games over fears of the virus.

The CDC updated its count of U.S. Zika cases this week. As of Wednesday, most of the 1,404 cases came from international travel. Fifteen cases are attributed to sexual transmission, and one case came from laboratory exposure. Only four states—Alaska, Idaho, South Dakota, and Wyoming—have yet to report a Zika infection.

But as the summer mosquito season swelters on, fears of local Zika transmissions grow.

On Tuesday, the Associated Press reported a woman in Miami-Dade County, Fla., had the first local transmission of the virus, indicating Zika-carrying mosquitoes had made their way across U.S. borders. But later reports backtracked the claim, indicating health officials have not determined whether the woman contracted the virus from travel or sex.

On Thursday, the Florida Department of Health reported a second suspected case of mosquito-borne Zika infection, this time in Broward County.

Florida health officials called on the CDC to assist with the investigation, fearing South Florida may be ground zero for America’s first local Zika outbreak. Neither the Florida Department of Health nor the CDC have confirmed whether either Zika infection occurred locally.

According to the CDC, in order to classify the case as America’s first local Zika transmission, officials must document at least two infections within a 1-mile radius within 30 days—both unrelated to recent travel or sex.