As of July 7, Zika has been diagnosed in 5,582* people, including 672 pregnant women, in Puerto Rico according to a new report published today in the Morbidity and Mortality Weekly Report (MMWR). Positive tests for people with suspected Zika virus infection have increased from 14 percent in February to 64 percent in June. Positive tests through blood supply screening also increased, reaching 1.8 percent during the latest week of reporting, which started on July 3.
“Puerto Rico is in the midst of a Zika epidemic. The virus is silently and rapidly spreading in Puerto Rico,” said Lyle R. Peterson, MD, MPH, incident manager for CDC’s Zika response and director, Division of Vector-Borne Diseases. “This could lead to hundreds of infants being born with microcephaly or other birth defects in the coming year. We must do all we can to protect pregnant women from Zika and to prepare to care for infants born with microcephaly.”
Many of the 5,582 people who tested positive for Zika virus infections were tested because they had symptoms of Zika. Because Zika infection during pregnancy can harm the developing fetus, pregnant women in Puerto Rico and other areas where Zika is spreading should be routinely tested during prenatal care whether or not they got sick. Of the 672 pregnant women, 441 (66 percent) experienced symptoms of Zika and 231 (34 percent) had no symptoms. Because approximately 80 percent of people infected with Zika do not have symptoms, the 672 pregnant women with evidence of Zika infection likely represent only a fraction of those who may be infected to date.
In addition, 21 people with confirmed or suspected Guillain-Barré syndrome in Puerto Rico had evidence of Zika virus infection or recent unspecified flavivirus infection, and one person died after developing severe thrombocytopenia (low blood platelet count).
Since Puerto Rico first reported local transmission of Zika virus in December 2015, it has become widespread on the island. People in 77 of 78 municipalities have tested positive for Zika virus infection. Large urban areas are most severely affected, with the largest numbers of diagnosed residents in the San Juan metropolitan area followed by the Ponce and Caguas metropolitan areas.
Outbreaks of mosquito-borne viruses tend to peak in the late summer and fall in Puerto Rico—hotter months with higher rainfall—raising concern that Zika will continue to spread and increase in the coming months. At the current trend, hundreds to thousands more pregnant women in Puerto Rico could become infected with Zika by the end of the year. There is also risk for more Guillain-Barré syndrome cases associated with Zika virus infection.
The situation in Puerto Rico warrants urgent, comprehensive action to protect pregnant women:
• The government of Puerto Rico and its municipalities can promote an integrated mosquito management program that includes reducing places with water where mosquitoes lay eggs, keeping mosquitoes out of houses with screens on windows and doors, and reducing the number of mosquitoes by using EPA-approved products. Everyone can follow these steps to help reduce the number of mosquitoes in and around homes.
• People who live in or travel to Puerto Rico should avoid mosquito bites by using EPA-registered insect repellents, wearing long-sleeved shirts and pants, and staying indoors in places with screens and air conditioning to the greatest extent possible.
• Pregnant women and their partners should use condoms and other barriers to prevent sexual transmission of Zika virus, or not have sex throughout the pregnancy.
• Couples who want to prevent or delay pregnancy should talk to their healthcare provider about safe and effective contraceptive methods.
• Clinicians who suspect Zika in patients who live in or have recently returned from areas with Zika, such as Puerto Rico, should report cases to public health officials.
CDC is working with Puerto Rico to provide services to protect pregnant women from Zika, support pregnant women who have been infected with Zika, increase lab testing, improve mosquito control, and provide access to contraception for women who choose to delay or avoid pregnancy. CDC is also currently sponsoring the public education campaign in Puerto Rico Stop Zika to raise awareness of Zika virus and personal protective actions residents can take.
*CDC only publishes data provided through ArboNET. Although Puerto Rico reports data to ArboNET, the Puerto Rico Department of Health reports cases from its own surveillance system, not ArboNET data. Differences in reporting between these surveillance systems contribute to the different numbers being reported by CDC and Puerto Rico.