First US case of Zika virus infection is identified in Texas

A traveler who had recently returned from Latin America to Texas has had Zika virus infection diagnosed, the first case to be recorded in the United States, local health officials report. The case was identified in Harris County, Texas, which includes the city of Houston.

Umair A Shah, executive director of Harris County Public Health and Environmental Services, warned travelers that Zika virus can now be found in much of the world. “We encourage individuals traveling to areas where the virus has been identified to protect themselves against mosquito bites, and to contact their healthcare provider immediately if they develop Zika virus-like symptoms,” he said.

The virus, a single stranded RNA virus of the Flaviviridae family, genus Flavivirus, was first discovered in the Zika Forest, Uganda, in 1947. Until recently it had been largely confined to Africa and Asia. The first locally acquired case in the western hemisphere, however, was reported on Easter Island in 2014. Since then it has spread rapidly, and locally acquired cases have now been reported in South America, Central America, the Caribbean, Mexico, and the US territory of Puerto Rico.1

The Zika virus is spread by the bite of a mosquito that has acquired the virus, usually by feeding on an infected person. The US Centers for Disease Control and Prevention estimates that one in five people infected with the virus becomes ill. Symptoms include fever, rash, joint pain, and conjunctivitis, as well as myalgia, headache, and vomiting. There is currently no vaccine to prevent Zika infection and no specific medicine to treat it. Treatment is symptomatic.

The illness is usually mild, and symptoms last for only about a week. Severe disease is uncommon, and reports of death are rare. In October, however, Brazilian health officials reported an unusual increase in cases of newborns with microcephaly in northeastern Brazil, and by 30 November 2015 more than 1200 cases of microcephaly, including seven deaths, had been reported. This represents a 20-fold increase in microcephaly rates, from 5.7 in 100 000 live births in 2010 to 99.7 in 100 000 live births.

In a number of these cases the virus was detected in blood and tissue samples from the newborn or in the amniotic fluid of pregnant women whose fetus had a diagnosis of microcephaly by ultrasound. Cases of neurological syndromes, including Guillain-Barré, have also been reported to be associated with Zika virus infection. The link between the infections and instances of microcephaly and neurological syndromes is currently under investigation.