Some mosquitoes in Miami Beach have tested positive for Zika, Florida officials say, marking the first time the virus has been found in groups of mosquitoes in the continental U.S.
Florida's Agriculture Department said Thursday that the virus was detected in three mosquito samples from a small area in Miami Beach, and authorities are blaming a particular flower for making mosquito control much more difficult..
"This find is disappointing, but not surprising," the state's agriculture commissioner, Adam Putnam, said in a release.
The number of non-travel-related Zika infections in humans has increased to 47 in Miami-Dade County since the first case was identified just over a month ago.
"This is the first time we have found a Zika virus positive mosquito pool in the continental United States," said Erin Sykes, a CDC spokeswoman.
The surveillance tests were conducted as part of an investigation by Florida's Health Department into local transmission of the virus.
It says more than 2,470 mosquito samples have been tested since May, and these three were the first to test positive.
One of the traps that tested positive was at the Miami Beach Botanical Gardens, where bromeliads bloom. The plants trap standing water in their cylindrical centres, providing excellent breeding areas for mosquitoes amid their colourful flowers and pointy leaves.
"Everyone should know by now that bromeliads are really problematic for us. These are probably the number one breeding area for mosquitoes," said Miami-Dade County Mayor Carlos Gimenez.
He said Miami Beach is removing all bromeliads from its landscaping, and urged residents across the county to either pull them out or rinse them after every rain.
Health officials say mosquito control is a key way to stem the outbreak, along with educating people about limiting their exposure to the insects.
Finding the virus in mosquitoes could help to target mosquito control efforts and confirms the insects are spreading the infection as suspected.
The illness spreads from people to mosquitoes to people again through bites, but the insects do not spread the disease to each other and their lifespan is just a few weeks.
Hurricane could complicate spraying
Hurricane Hermine, set to cause flooding and damage when it hits Florida overnight, could complicate efforts to fight Zika in Florida, experts in infectious diseases and mosquitoes said.
Once the hurricane passes, the remaining water will provide breeding sites for mosquitoes, said William Schaffner, a professor of infectious diseases at the Vanderbilt University School of Medicine in Nashville.
"People around their homes will be worried about themselves and their families and neighbours rather than looking for
mosquito breeding sites," Schaffner said. "Emergency responders will be focused on things other than mosquito abatement."
High winds from the hurricane could also prevent aerial spraying with pesticides to keep mosquito populations down, said Joseph Conlon, a retired U.S. Navy entomologist who serves as technical adviser for the American Mosquito Control Association.
Elsewhere on Thursday, China intensified its checks on people and goods arriving from Singapore, as an outbreak of the Zika virus in the small city-state was confirmed to have spread to at least one person in neighbouring Malaysia.
The government said earlier that about half of the cases it was discovering were foreigners, mainly from China, India and Bangladesh, and most had already recovered. Many of them are believed to be among the hundreds of thousands of migrant workers in Singapore's construction and marine industries.
The virus, which has spread through the Americas and the Caribbean since late last year, is generally a mild disease but has been linked to microcephaly — a severe birth defect in which babies are born with abnormally small heads and underdeveloped brains.
Zika is carried by mosquitoes, which transmit the virus to humans, though a small number of cases of sexual transmission of the virus have been reported in the Americas.
There is no vaccine or treatment for Zika, which is a close cousin of dengue and chikungunya and causes mild fever, rash and red eyes. An estimated 80 per cent of people infected have no symptoms.