August 10, 2016

When the Centers for Disease Control and Prevention (CDC) released its July 29 update on the state of Zika infection in Puerto Rico, the news was not good for the island or its tourism industry.

For much of the time since the virus was discovered in Puerto Rico last November, Zika infections had been relatively stable, though the number gradually increased each month. That changed in April. Since then, week after week, the number of new infections in Puerto Rico has grown exponentially.

In February the official count of new confirmed and presumptive cases of Zika on the island was 291. By June, that number had jumped nearly eight-fold, to 2,612. As of July 7, a total of 5,582 confirmed and presumptive Zika cases had been reported in Puerto Rico, including 672 pregnant women. Between February and June, the number of pregnant women testing positive increased almost six-fold.

In the Hot Seat

The Puerto Rican government's prevention campaign, which emphasizes controlling the mosquitoes that carry the disease and educating residents and visitors about how to protect themselves from bites, appears not to be working. Based on previous patterns of similar outbreaks on the island, the CDC reported that "the Zika virus outbreak exhibits no signs of abating."

Puerto Rico is by no means the only destination dealing with concerns about the spread of Zika. The CDC has issued travel notices regarding Zika for 25 nations in the Caribbean, 12 countries in South America and in Mexico, among other places.

In fact, in an unprecedented move last week, the agency advised pregnant women to avoid Miami's Wynwood neighborhood, where the first locally transmitted cases of Zika in the U.S. mainland have been identified.

For public health officials, tracking and containing Zika is difficult because while Zika infections in pregnant women have been associated with microcephaly, a birth defect in which an infant is born with a smaller-than-normal head, severe neurological damage and a range of long-term problems, most people who contract the disease exhibit no symptoms at all.

Four out of five Zika patients are believed to be asymptomatic, and among those who do display symptoms, it often manifests as a mild illness that includes fever, rash, joint pain and conjunctivitis.

Emily Toth Martin, a professor of epidemiology at the University of Michigan School of Public Health, said last week that when the CDC reports a total of 5,582 Zika cases in Puerto Rico, "there are probably a lot more asymptomatic cases than what is encompassed in that number."

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