Dallas County officials said Tuesday that a traveler to Venezuela they called Patient 0 had sex with Patient 1 after returning home, and now both have tested positive for the Zika virus.
The two cases were the first reported in North Texas.
“Now that we know Zika virus can be transmitted through sex, this increases our awareness campaign in educating the public about protecting themselves and others,” said Zachary Thompson, DCHHS director. “Next to abstinence, condoms are the best prevention method against any sexually transmitted infections.”
The Dallas cases came a day after the World Health Organization declared a public health emergency because of the rapid spread of the Zika virus across Central and South America.
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WHO officials estimate there could be up to 4 million cases of Zika, which has has been linked to birth defects, in the Americas next year.
In Texas, the first six travel-related cases of Zika occurred in the Houston area before the case was confirmed in Dallas.
“Education and awareness is crucial in preventing Zika virus,” said Dr. Christopher Perkins, DCHHS medical director/health authority. “Patients are highly encouraged to follow prevention recommendations to avoid transmitting and spreading Zika virus.”
Still, experts are waiting to see if it eventually becomes transmitted in Texas like the West Nile virus or if will it be more like other mosquito-borne viruses, such as chikungunya and dengue fever, that have had sporadic outbreaks but haven’t become established locally.
I think this summer will be the litmus test, especially with all of the travel between the U.S. and Brazil.
Texas A&M Agrilife entomologist Mike Merchant
Not everyone is convinced about sexual transmission of the virus.
Dr. George Sealy Massingill, chairman of obstetrics and gynecology at John Peter Smith Health Network in Tarrant County, called the Dallas County sexual transmission a “postulated case.”
“So far, that’s their best guess how this happened,” he told the Star-Telegram Tuesday evening. “It’s hard to go back and say that A caused B.”
Since Patient 0 traveled to a place where the Zika virus is common, health officials are “postulating” that the virus was transmitted to Patient 1 by sex, but researchers aren’t certain, he said.
“You get it mostly from getting bitten by mosquitoes,” Massingill said. “Don’t get bitten by mosquitoes and this won’t be a problem.”
There is one previous case of possible sexual transmission — a Colorado husband, a mosquito researcher who became infected in Senegal, and his wife came down with Zika virus in 2008 — but proof of the cause has been elusive.
A spokesman for the Texas Department of State Health Services said, “We think it’s likely that this [Dallas-area] case was sexually transmitted, but we’ll be looking for more information.”
Texas A&M Agrilife entomologist Mike Merchant thinks we won’t have to wait long to find out if Zika will gain a foothold locally.
“I think this summer will be the litmus test, especially with all of the travel between the U.S. and Brazil,” Merchant said.
The mosquito believed to be the main carrier of Zika is the aedes aegypti, and it tends to bite during the daytime. During winter, it is not active across North Texas, but that will change as the temperature warms up in the coming months.
“You're definitely not going to see too many mosquitoes this time time of year, but when the temperatures starts staying consistently above 60 or 70 degrees, they’ll become active,” Merchant said.
Merchant also said there’s a question whether the aedes albopictus mosquito, which is also common in North Texas, can also carry Zika. The research hasn’t been conclusive, but there are data that show it can also carry the Zika virus.
Both the aedes aegypti and aedes albopictus can carry chikungunya.
The West Nile virus is carried by culex mosquitoes, which bite at night.
More cases expected in U.S.
A University of North Texas Health Science Center professor who has overseen a program to test and trap mosquitoes in Tarrant County for West Nile is also concerned about Zika.
“Based on the increase of the virus circulation in the Americas, more imported cases of Zika virus are expected in the U.S. and Texas,” said Joon Lee, a UNT Health Science Center associate professor of environmental and occupational health sciences.
“Increased awareness of travelers and doctors on the virus, and appropriate action of returned travelers from the areas with the virus circulation would be essential to minimize the risk of local transmission,” Lee said in an email.
Last month, the Centers for Disease Control and Prevention issued interim guidelines and travel notices for pregnant women who have visited countries reporting Zika or for those who are considering traveling to Central and South America as well as the Caribbean. On Monday, the CDC also issued Zika travel alerts for American Samoa, Costa Rica, Curacao and Nicaragua.
The virus has been linked to an increase in the number of babies born with small heads since it arrived in Brazil last year, prompting the WHO to convene an emergency meeting in Geneva.
It’s the first international emergency that has been declared by WHO since the Ebola outbreak in 2014 in West Africa that killed more than 11,000 people, including a man in Dallas who had flown in October of that year to the United States from Liberia, setting off a monthlong public health crisis in the region.
WHO officials say it could be six to nine months before science proves or disproves any connection between Zika and the birth defects in Brazil, according to The Associated Press.
‘Need to raise awareness’
At Cook Children’s Medical Center in Fort Worth, Dr. Mary Suzanne Whitworth, an infectious diseases specialist, doesn’t believe the WHO declaration will change anything locally. Like others, she isn’t sure what will happen with Zika.
“I don't think anyone knows,” Whitworth said. “We can all speculate. The same mosquitoes that carry Zika carry chikungunya and dengue fever. If you had asked us about five years ago, I think we all would have said it would be here. Neither dengue or chikungunya have spread significantly.”
Zika was first identified in 1947 in a Ugandan forest, but until last year, it wasn’t believed to cause any serious effects; about 80 percent of infected people never experience symptoms. The virus has also been linked to Guillain-Barre syndrome, which causes muscle weakness and nerve problems.
Zika virus hasn't been proved to cause microcephaly or Guillain-Barre syndrome. Still, health officials in many Zika-affected countries are warning pregnant women to avoid mosquitoes and even suggesting women delay pregnancy until the outbreak is over.
Microcephaly “is not usually fatal, but it is consistent with diminished IQ and learning disabilities,” JPS’ Massingill said.
Researchers don’t have definite percentages of pregnant women infected by the virus who bore children with microcephaly, he said. And doctors cannot give reliable odds to a woman that if she becomes pregnant “what the likelihood is that the baby will have problems,” Massingill said.
There isn’t even reliable knowledge of how long the virus lives in a human’s system, he said.
Massingill, who is also president-elect of the Texas Association of Obstetricians and Gynecologists, said he participated in a conference call Tuesday organized by the Texas Medical Association with other doctors about recommendations they and the CDC can come up with for women and their health care providers.
For now, the only advice is that pregnant women shouldn’t travel to places where the virus is an issue and should avoid exposure to mosquitoes in general.
The CDC said Tuesday that it will issue guidance in coming days on prevention of sexual transmission of Zika virus, focusing on the male sexual partners of women who are or may be pregnant.
Last week, the JPS Health Network started asking patients Zika-specific travel questions, spokeswoman Kris Newcomer said.
Those places for now are the Americas and the Caribbean, she said.
If the patients reply yes, they will be evaluated for symptoms of the virus, which includes fever, sore joints and conjunctivitis (pinkeye).
Staff writer Monica Nagy contributed to this report.