Pennsylvania health officials have reported the state’s first case of Zika found by testing donated blood.
The virus is linked to serious birth defects, and for months donations have been tested for it, with any that show signs of Zika removed from the blood supply.
“We get a lot of false positives,” said Pennsylvania Department of Health spokeswoman April Hutcheson. “This was the first case of a true positive.”
She said the donor “acquired Zika through travel outside the continental United States,” and that the finding does not mean the virus is being transmitted by mosquitoes here.
To date, transmission by mosquito in the continental United States has been reported only in small parts of Florida and Texas.
Officials have said Pennsylvania’s 224 suspected or confirmed cases since early last year were attributed to travel to infected areas or sex with someone who traveled there or, in one case, an accidental needle stick in a research lab.
CDC records show that the virus was found in eight states by testing donated blood in 2016.
Although Zika has been spread by blood transfusion in Brazil, the agency said, no similar cases have been confirmed in the United States.
So far this year, the agency has reported Zika findings from one blood donor each in Pennsylvania, California, Louisiana, New York, Texas and West Virginia, and three in Florida.
The CDC has a travel alert for places where mosquitoes could spread the virus to people.
It includes Mexico, Puerto Rico, the Dominican Republic, nearly all of central and south America, about half of the African continent, India, much of Africa and many island countries of southeast Asia.
Health officials did not say where the donor was from in Pennsylvania, but Central Pennsylvania Blood Bank and Lancaster General Blood Donor Center both said testing has not found Zika in any donations there.
People are asked to defer donation if screening reveals that they have recently traveled to areas where mosquitoes are transmitted Zika.
Lancaster General spokeswoman Mary Ann Eckard said about 50 people have deferred donating because of travel. Central Pennsylvania Blood Bank Jay Wimer said it has not seen a significant number of deferrals related to Zika.
LNP reported last that at least 29 pregnant women in Lancaster County have been infected by or exposed to Zika.
Reporting methods leave it unclear whether any local babies have had Zika-related birth defects, although local providers said they had not seen any.
One type of mosquito that can spread the disease has been found in Lancaster County, but so far none of the mosquitoes have tested positive for Zika.