Health officials in Texas have recently reported the first known case of sexual transmission of Zika virus in the United States, a day after the World Health Organization declared an international public health emergency.
The Dallas County Health and Human Services said the patient contracted the virus from a sexual partner who was ill after being infected while traveling to Venezuela, which has a Zika outbreak. The person infected did not travel to the South American country, county health officials said.
The Texas Department of State Health Services was slightly more cautious in its assessment, saying in a statement, “Case details are being evaluated, but the possibility of sexual transmission from an infected person to a non-infected person is likely in this case.”
The virus, linked to severe birth defects in thousands of babies in Brazil, is spreading rapidly in the Americas, and WHO officials have expressed concern that it could hit Africa and Asia as well. Zika had been thought to be spread by the bite of mosquitoes of the Aedes genus, so sexual contact as a mode of transmission would be a potentially alarming development.
After this case, the CDC advised men to consider using condoms after traveling to areas with the Zika virus. Pregnant women should avoid contact with semen from men exposed to the virus.
Previously, international health officials had noted one U.S. case of possible person-to-person sexual transmission. But the Pan American Health Organization said more evidence was needed to confirm sexual contact as a means of Zika transmission. The medical literature also has one case in which the virus was detected in semen.
The virus has been reported in more than 30 countries and linked to microcephaly, in which babies have abnormally small heads and improperly developed brains.
The American Red Cross on Tuesday asked blood donors who have traveled to Zika virus outbreak areas such as Mexico, the Caribbean, or Central or South America to wait at least 28 days before donating. However, the risk of transmitting the virus through blood donations remained “extremely” low in the continental United States, the disaster relief agency said.
The WHO has said the virus could infect 4 million people in the Americas. It said on Tuesday it launched a global response unit to fight the mosquito-borne virus.
“Most important, we need to set up surveillance sites in low- and middle-income countries so that we can detect any change in the reporting patterns of microcephaly at an early stage,” Dr. Anthony Costello said in Geneva. Costello is WHO’s director for maternal, child and adolescent health.
Brazil is the country hardest hit by Zika. In an address to a joint session of Brazil’s Congress, President Dilma Rousseff said her government will spare no resources in mobilizing to combat the mosquito that transmits the virus. With no vaccine or treatment for Zika, efforts to curb its spread have focused on eradicating mosquito breeding sites.
Brazil, which has more than 4,000 suspected cases of microcephaly that may be linked to Zika, is scheduled to host the Olympics in Rio de Janeiro in August.
Rousseff also said Brazil and the United States will enter a partnership to develop a Zika vaccine as soon as possible to stem the spread of the virus.
French drugmaker Sanofi SA on Tuesday announced that it has launched a project to develop a vaccine against the virus, the most decisive commitment yet by a major vaccine maker. The company said its Sanofi Pasteur vaccines division would use its expertise in developing vaccines for similar viruses such as yellow fever, Japanese encephalitis and dengue.
Other companies also joined the race on Tuesday to develop a vaccine.
