First Zika Virus Case in Continental United States Confirmed in Texas

Janis C. Kelly

January 11, 2016

Zika virus, a mosquito-borne infection believed to cause microcephaly in infants born to infected mothers, has crossed from Latin America into Texas, experts reported today.

The case of Zika in a traveler recently returned from El Salvador was confirmed through investigations by Harris County, Texas, health officials and the Centers for Disease Control and Prevention (CDC). The case is expected to result in major new surveillance and vector-control initiatives.

Peter Hotez, MD, dean of the National School of Tropical Medicine at Baylor College of Medicine, president of the Sabin Vaccine Institute, and Texas Children's Hospital Endowed Chair of Tropical Pediatrics, Houston, told Medscape Medical News, "There is a perfect storm brewing for Zika virus in the US. I was never worried that Ebola would take off here, but I am worried about Zika. We have 2 species of Aedes mosquitoes that can transmit Zika in our area. We also have high levels of poverty, resulting in people living without window screens and near discarded tires and other water-catching containers where the mosquitoes can breed."

Dr Hotez said that Zika infection usually produces nonspecific, influenza-like symptoms in pregnant women, with the associated birth defects becoming apparent only 9 months later.

"By that time, it is too late," Dr Hotez said. "This first case of Zika infection in Harris County is a wake-up call, a warning that we should immediately start implementing programs of active surveillance. As we move into the spring and summer months, if we start seeing cases among people who have never traveled outside of the country, we need to implement aggressive mosquito control measures as well as health advisories for people to implement personal protection measures."

Such measures would include emptying or covering any container that could hold water (tires, buckets, flower pots, bird baths, etc), and repairing leaks or taps on septic tanks. They would also include using screens and having air conditioning if possible. Dr Hotez said that people likely to be exposed to mosquitoes should use one of the CDC-recommended insect repellents registered with the US Environmental Protection Agency, such as DEET, picaridin, oil of lemon eucalyptus, or IR3535. When they are used with sunscreen, the CDC recommends that the insect repellent be applied after the sunscreen. Dr Hotez said that mosquito repellent should be reapplied every couple of hours, and that people anticipating mosquito exposure should also consider permethrin-treated clothing and gear.

Umair A. Shah, MD, MPH, executive director of the Harris County (Texas) Public Health & Environmental Services agency, told Medscape Medical News that the Texas patient developed typical symptoms of rash, muscle aches, and joint pain while visiting El Salvador in November 2015 and sought medical care when symptoms persisted after return to the United States in December 2015. Screening tests and further laboratory studies resulted in notification from CDC of a "preliminary positive for Zika virus."

Dr Shah's agency promptly alerted area physicians about the Zika case. Dr Shah said, "We urge physicians to keep Zika in their differential diagnosis, along with chikungunya, dengue, and West Nile, when considering possible mosquito-borne viruses, especially in patients who have traveled to a country where Zika is present. The common denominator for these diseases is mosquitoes." Countries currently known to have Zika infections include those in tropical Africa, Southeast Asia, the Pacific Islands, and Central and South America. The first case of Zika in Puerto Rico was reported in December 2015.

Dr Shah warned that although there has been no local transmission of Zika as yet in the continental US, areas along the Gulf Coast have populations of the two species of Aedes mosquitoes that serve as vectors for Zika virus. He said that a patient with sufficiently high Zika viral load could, in theory, pass Zika to one of these mosquitoes.

"My advice for travelers is to Prevent and Present: Prevent getting bitten by mosquitoes, and if you do develop symptoms, present yourself promptly for medical care. If you have symptoms, don't ignore them," Dr Shah said.

Finally, Dr Hotez stressed that the confirmed case of Zika in Texas highlights the need to immediately deploy research support and resources to develop a vaccine against the virus.

Heightened international concern about Zika was driven not by its relatively mild effect on infected adults, who typically recover in about a week, but by its devastating effect on babies in utero. In Brazil, cases of microcephaly, in which the brain does not develop fully before birth, surged from an average 150 per year to almost 4000 cases in 2015. Dr Regina Coeli, a pediatric infectologist at Oswaldo Cruz Hospital in Recife, the region worst affected in Brazil, told BBC World Service that a link between Zika and microcephaly was established when Zika was found in the amniotic fluid of two women and in the brain and heart of an affected infant.

The fast-moving epidemic of Zika in Brazil led Brazilian health authorities to advise women to delay conception to reduce the risk of bearing children with devastating birth defects.

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