We just learned lessons about our preparedness (or lack thereof) in detecting and managing one virus in the form of Ebola, and now we have another? Now it seems, along with everything else, emergency physicians must function as frontline epidemiologists, identifying potentially dangerous infections. Welcome to the new millennium of emergency medicine.

Zika Basics

Zika virus, a flavivirus transmitted mainly by mosquitos, is another in a line of emerging infectious diseases (EIDs) making new or return appearances in the United States. Zika can also be spread sexually (although the ease of transmission is not known) and through blood transfusions (a particular problem in outbreak areas). Most areas of South America, Central America, and Mexico are currently experiencing the largest known outbreak of Zika viral infection. To date, more than 150 cases of Zika have been detected in the continental United States. Current data suggest that at least nine of these cases (5.8 percent) are in pregnant women. All of these have been travel related in people returning from outbreak areas. About 107 endemic (locally transmitted) cases acquired by mosquito bites have been reported in Puerto Rico and the US Virgin Islands. In outbreak areas, the proportion of the population infected varies from 70 percent to 1.2 percent based on multiple factors. The vector mosquitos required to transmit Zika are already endemic in the South, Midwest, and Eastern United States. The World Health Organization predicts that Zika will likely be endemic in most of the United States within two years.

Zika is related to dengue, Chikungunya, yellow fever, Japanese encephalitis, and tickborne encephalitis. It usually causes a mild disease resulting in only rare hospitalizations or deaths. However, during the current outbreak, some very astute physicians in Brazil noted a sharp increase in the number of births with severe microencephaly.

The symptoms of Zika include macular or papular rash (90 percent), subjective fever (65 percent), arthralgia (65 percent), conjunctivitis (55 percent), myalgia (48 percent), cephalgia (45 percent), retro-orbital pain (39 percent), dependent edema (19 percent), and vomiting (10 percent). The presence of conjunctivitis and absence of hemorrhage are the most useful clinical indicators in differentiating Zika from dengue and Chikungunya infections (see Table 1). Zika causes minimal disease, with only one in five infected people developing symptoms. Other viral diseases such as dengue and yellow fever are also moving into the United States and are of much greater clinical concern, except for the question of pregnancy.