A Tropical Third Wave – Dengue, Chikungunya and Now Zika
Recent news has highlighted a dramatic rise in the incidence of microcephaly – congenital, abnormal smallness of the head and associated incomplete brain development – in children born to mothers who had been infected with the Zika virus. This phenomenon caused the U.S. Centers for Disease Control and Prevention (CDC) to issue a rare travel advisory on some 45 nations for pregnant women and women who may become pregnant.
First observed in Uganda in 1952, Zika is a flavivirus related to yellow fever, West Nile, Chikungunya and dengue; and like its cousins is transmitted primarily by Aedes aegypti mosquitoes.
Zika is generally mild and lasts two to seven days. The main symptoms are low-grade fever, conjunctivitis, temporary arthritis/arthralgia (typically of the hands and feet) and a rash that often starts on the face and then spreads across the body. Recent news of Zika is noteworthy, however, for two significant reasons. The sudden increase in cases of microcephaly is remarkable. Microcephaly is rare; occurring from 1 per 6200 to 8500 births. The rate among Brazilian mothers who have experienced Zika fever has been approximately 21 times that. Prognosis for microcephaly varies, and is impacted by other medical conditions. In general, however, life expectancy for children with microcephaly is reduced, and the prospects of attaining normal brain function is poor.
The other concerning aspect is the spread of the disease. Originating in Sub-Saharan Africa, Zika has spread across Africa, to Asia and the Pacific Islands, and now to South American and the Caribbean. The cases diagnosed in the continental U.S. and Puerto Rico have been in women who traveled to impacted areas. It is likely, though, that transmission will eventually occur in the U.S., as has happened with dengue and West Nile, as a result of human travel, global movement of goods and an increase in the habitat range of Aedes aegypti mosquitoes due to climate change.
There is no vaccine or prophylactic medication available to prevent Zika virus infection. CDC recommends pregnant women consider postponing travel to areas where Zika virus transmission is ongoing. If living in or visiting such an area, avoiding mosquito bites offers the best alternative.
Mosquitoes that spread Zika virus bite both indoors and outdoors, mostly during the daytime; therefore, it is important to ensure protection from mosquitoes throughout the entire day. Wear long-sleeved shirts and long pants, use U.S. Environmental Protection Agency (EPA)–registered insect repellents, use permethrin-treated clothing and gear and stay and sleep in screened-in or air-conditioned rooms. CDC guidelines state insect repellents containing DEET, picaridin and IR3535 are safe for pregnant women when used as directed on the product label.