The outbreak of Zika virus in Brazil and other countries has raised concern that the pathogen could start spreading widely in the United States as well. But federal health officials and other infectious disease specialists say so far that seems unlikely.
"Based on what we know right now, we don't think that widespread transmission in the United States is likely," says Dr. Beth Bell, director of the National Center for Emerging and Zoonotic Infectious Diseases at the Centers for Disease Control and Prevention.
There are several reasons for Bell's cautious optimism that isolated cases that show up in the U.S. could be contained. The first is that the two species of mosquitoes that could be capable of transmitting the virus, Aedes aegypti and Aedes albopictus, live mostly in the southern, more tropical parts of the U.S. That makes it likely that transmission would be limited primarily to these areas. And for various reasons, the chain of events and conditions the virus needs in order to spread is more easily disrupted in the U.S. than elsewhere.
For example, many people in the U.S. have air conditioning in the summer, so aren't as likely to leave windows open at the times of day when mosquitoes are especially active. Open windows also tend to have screens. And many counties and other municipalities spray to kill mosquitoes and are vigilant in trying to eliminate pools of standing water where the insects can breed.
"These are all conditions that make it less likely for ongoing, large-scale spread to occur," Bell says.