To gain a more complete picture of the impact of Zika virus infection during pregnancy, the Centers for Disease Control and Prevention (CDC) has begun reporting the total number of pregnant women with Zika virus infection from two newly established enhanced surveillance systems: the U.S. Zika Pregnancy Registry and the Puerto Rico Zika Active Pregnancy Surveillance System. As of May 12, 2016, the two Zika virus infection surveillance systems are monitoring 157 pregnant women in the U.S. states and 122 pregnant women in the U.S. territories with laboratory evidence of possible Zika virus infection, a total of 279 pregnant women in U.S. states and territories.
These new numbers reflect a broader group of pregnant women—those who have any laboratory evidence of possible Zika virus infection, whether or not they recalled having symptoms—compared with the previously reported numbers. This new way of reporting the numbers of infected women aligns with recommendations for ongoing monitoring of pregnancies at risk for poor outcomes associated with Zika virus infection, based on scientists’ current understanding of the effects of the Zika virus during pregnancy.
Until now, the CDC has reported the number of people with Zika virus disease using a case definition established in consultation with the Council for State and Territorial Epidemiologists, which included only individuals who had laboratory test results and symptoms or pregnancy complications consistent with Zika virus infection. Recent published reports indicate, however, that some pregnant women with laboratory evidence of a recent Zika infection but without symptoms have delivered infants with microcephaly and other serious brain defects. Therefore, the CDC is now reporting the numbers of pregnant women with Zika virus infection from the U.S. Zika Pregnancy Registry and the Puerto Rico Zika Active Pregnancy Surveillance System.
The CDC told reporters on a conference call that, so far, fewer than a dozen of the infected pregnant women it has tracked in the U.S. and Puerto Rico have had miscarriages or babies born with birth defects. Brazil, the country hardest hit by Zika to date, has confirmed more than 1,300 cases of microcephaly linked to the virus.
The CDC also told reporters that it has dramatically increased its testing capacity for the Zika virus in the U.S. as it girds for an increase in cases during the summer mosquito season when Gulf Coast states, such as Florida, Louisiana, and Texas, are expected to be on the front lines of local transmission.
So far, almost all the Zika cases in the continental U.S. have been in people returning from countries where Zika is prevalent, such as Brazil, with a small number attributed to sexual transmission by such travelers.
Officials say only about 20% of people with Zika virus infection show common symptoms, such as fever, rash, joint and muscle pain, and conjunctivitis.