The United States has experienced its first Zika infection appearing across state lines, but health experts say there is little danger the country will experience a widespread outbreak of the disease.
That’s because of public health programs in the United States, as well as the low odds of the right species of mosquito contracting the virus from infected humans in this country.
Experts told Healthline the low risk of transmission should calm any fears from news early this week that a Texas man was diagnosed with Zika.
Texas health officials said the man had traveled to a Miami neighborhood in South Florida where Zika has spread, and then he returned home.
“It’s not surprising that he got the disease and left the state,” said Dr. Lee Norman, chief medical officer at the University of Kansas Hospital. “It would be difficult for it to spread in Texas, so the risk is very low.”
The right conditions
For the Zika virus to spread, you need a significant number of people with the illness in their bloodstream, and a large number of the right species of mosquitoes in a concentrated area.
Zika is transmitted only by the Aedes species mosquito, a notorious daytime biter. Other types of mosquitoes don’t carry the disease.
The virus also cannot be transferred from mosquito to mosquito. A mosquito needs to bite a human infected with the virus.
There’s a short window of time on both ends.
The virus is usually only active in a person for a few weeks. In addition, most mosquitoes live for less than a month.
Although the Zika virus can be transmitted via semen during sex, the primary transmission vehicle is an infected mosquito.
The short time period for transmission makes most areas of the United States low risk regions.
For example, Norman said, the infected man in Texas probably no longer has Zika in his blood stream. So, even if he was bitten by an Aedes mosquito now, that insect wouldn’t contract the virus.
The right conditions for widespread infection have been present in Brazil, where close to 100,000 cases have been reported.
They are also present in Puerto Rico, where more than 6,000 locally acquired cases have been diagnosed.
“There are mosquitoes everywhere and a lot of people have the virus,” said Norman. “It’s the right brew.”
To a lesser degree, the conditions are present in the Wynwood neighborhood of Miami, where more than two dozen people have been diagnosed with the disease.
There have also been concerns the floods in Louisiana could produce enough standing water for the Aedes mosquito to breed. However, this week health officials said the West Nile virus is probably a bigger threat in Louisiana.
In the United States, preventative measures are securely in place to prevent the right conditions for Zika to spread rapidly.
First, there are mosquito eradication programs in most areas of the country.
These include spraying, screens on doors and windows, and insect repellant. Norman noted that applying repellant is not part of the common culture in places like Puerto Rico.
In addition, people who do contract the virus receive treatment, and are generally isolated from the rest of the population as well as local mosquitoes.
Benjamin Haynes, a spokesman for the U.S. Centers for Disease Control and Prevention (CDC) noted the Aedes mosquito also carries the virus for dengue fever and chikungunya.
Despite a dengue outbreak this year in Hawaii, Haynes told Healthline past outbreaks of those diseases have been “relatively small and limited to a small area.”
The Zika virus actually creates a relatively mild illness in most people. The biggest danger is for pregnant women who can transmit the virus to their unborn child. In a fetus, the virus can cause birth defects, in particular the brain deformity known as microcephaly.
With that in mind, scientists are also getting involved in Zika prevention.
Earlier this month, the Food and Drug Administration (FDA) approved the trial release in Florida of genetically altered male Aedes mosquitoes. The idea is to have these mosquitoes mate with female mosquitoes and then produce offspring that die before they reach adulthood.
The experiment is scheduled to start in the Florida Keys, but so far an outcry from local residents has delayed its implementation.
Other scientists also began human trials early this month on a Zika vaccine.
About 80 healthy volunteers between the ages of 18 and 35 at three study sites are participating in the phase I trial.
The results of the phase I trial, which examines the safety of the vaccine, are expected in January. If the results are favorable, a phase II trial to examine the vaccine’s effectiveness would begin in Zika-endemic countries.
Dr. Asim Jani, M.P.H., F.A.C.P., an infectious disease specialist at Orlando Health in Florida, said vaccine trials can be complex.
There are funding issues for Zika prevention measures due to congressional inaction on the vaccine program. That was temporarily resolved this month when federal officials transferred $81 million from other programs to the vaccine research.
Nonetheless, Jani told Healthline the United States has a good record when it comes to vaccines.
“We have had success when it comes to research of vaccines,” he said.