Bad news for those who think the Zika virus will go away when the weather cools.
The virus, spread via mosquitoes and linked to the birth defect microcephaly, could linger in parts of the U.S. during the colder winter months. And a major outbreak in other parts of the world could lead to more travel-related cases in the U.S.
“Zika is likely going to be endemic in this hemisphere,” said Dr. Tom Frieden, director of the Centers for Disease Control and Prevention, during a Friday briefing with reporters. “It is likely to spread on some level for years to come. That is one of the reasons that a vaccine is so important and mosquito control is so important.”
Zika is spreading in the U.S. through mosquito bites in Miami and sporadically in other parts of Florida. More than 50 cases of local transmission have been found.
U.S. mosquito season usually continues through October, meaning that conceivably mosquitoes that spread the virus will die out as the weather cools.
However, some parts of the U.S. have mosquitoes longer in the year. Frieden used the Florida Keys as an example, saying that it “actually continued through one year and into the next.”
He noted that the Keys went through an outbreak of dengue in 2009, which is a virus that is also spread via bites from the Aedes aegypti mosquito. The outbreak continued during the off-season at a “lower rate through the year and continues into the next year.”
The Florida Keys have not had any cases of local transmission of Zika, but did have a new dengue case pop up in June.
He added that the next mosquito season isn’t far away, and that the U.S. territory of Puerto Rico started seeing cases in January.
The winter could lead to a higher amount of travel-related Zika cases, Frieden said.
The U.S. has found almost 3,000 cases of Zika, almost all of which are people who got the virus in another country or territory. As of Sept. 7, health officials have identified 671 pregnant women who may have Zika and17 cases of microcephaly, according to the CDC.
The virus has been spreading in more than 50 countries and territories.
Countries in South America such as Colombia and Brazil have had the largest outbreaks, with Brazil seeing more than 1 million cases.
However, the virus is starting to spread in some parts of Asia.
Singapore has been battling the Zika virus since late August, with government officials confirming another 12 cases on Friday. The additional cases bring the total past 300.
“If it spreads widely in Asia and Africa, that will increase further the number of U.S. travelers that will contract Zika abroad,” Frieden said.
Congress has yet to agree on how to fund a robust response. A standoff has lingered over a $1.1 billion package that passed the House but stalled in the Senate due to objections from Democrats to provisions that did not include funding for Planned Parenthood centers in Puerto Rico.
Meanwhile, some of the longer-term projects to tackle Zika could suffer from the standoff. National Institutes of Health offiicials say they may not be able to continue a major trial of a possible vaccine, and Frieden said the CDC would run out of appropriated Zika funding by the end of the month.
