U.S. health officials said Friday that four cases of Zika virus were transmitted locally by mosquitoes in Miami, the first evidence of the virus spreading that way in the continental U.S.
Previous cases have been caused by travel to affected areas or sexual contact with an infected person, and the report from Florida suggests that outbreaks of the virus could become common in some parts of the country, rather than just being imported from abroad.
“As we have anticipated, Zika is now here. Everything we’ve seen so far indicates to us that this is mosquito-borne transmission,” U.S. Centers for Disease Control and Prevention Director Tom Frieden said Friday on a call with reporters. While the findings are concerning, and more cases could be found, health officials “don’t expect widespread transmission in the continental U.S.,” he said.
The Florida Department of Health is investigating a small area in Miami, just north of downtown, where it “believes that active transmission of the Zika virus is occurring,” the state health agency said in a statement. The area, which is about a square mile, includes the Wynwood neighborhood — known for its art district and restaurants. One of the cases involves a woman and the other three involve men.
Because symptoms are typically mild, it’s possible that the disease has already spread through mosquitoes in other places or that the infection is more widely present and transmitting in Florida without health officials being able to confirm it. None of the four Florida patients exhibited symptoms.
“There may well be more cases that we’re not aware of right now because most people infected with Zika don’t have symptoms,” Frieden said Friday.
Florida Governor Rick Scott said Florida has a good track record of fighting mosquito-borne viruses and has directed health officials to increase mosquito abatement efforts in the affected areas.
Florida is battling the virus with its own resources and additional funds from the CDC, which add up to about $12 million, according to Benjamin Haynes, a spokesman for the agency. Additionally, Scott said in June that he would use his executive authority to allocate $26.2 million in state funds for Zika preparedness, prevention and response in Florida.
The CDC is “scrambling to come up with money” and prepare states as lawmakers left for recess after once again failing to pass a $1.1 billion spending package to combat the spread of the virus, Tom Skinner, a spokesman, said in a telephone interview last week.
President Obama was briefed this morning and has directed his team to monitor and assist the investigations. The news should be “a wake-up call to Congress to get back to work,” Deputy Press Secretary Eric Schultz said during a press briefing on Friday.
The virus has spread rapidly through the Americas since Brazil became the nexus of cases in May 2015. The number of infected people in U.S. states and territories rose to more than 6,400, according to the latest figures from the CDC. In U.S. mainland, there are 1,658 confirmed cases of Zika virus, including 433 pregnant women, and most are related to international travel. New York has the highest number of travel-related Zika cases, followed by Florida, the data show.
In Florida, officials are going door-to-door in affected areas to talk with residents and collect samples, and they have interviewed and tested more than 200 people. Blood centers in the Miami and Fort Lauderdale areas have been asked to stop collecting blood until they can screen donations for Zika, the U.S. Food and Drug Administration said in a statement on Thursday.
Zika can provoke serious brain defects in babies born to infected mothers. Researchers and officials also have found links between Zika and Guillain-Barré syndrome, a condition in which the immune system attacks nerves, causing temporary paralysis. The World Health Organization declared Zika a global public health emergency in February.
There are no drugs to treat Zika and no vaccine to prevent it, though drugmakers are working on it. Sanofi plans to harness its work against dengue, a virus from the same family, to develop a vaccine against Zika virus.