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| Severina Raimunda holds her granddaughter Melisa Vitoria, left, who was born with microcephaly and her twin brother Edison Junior at the IMIP hospital in Recife, Pernambuco state, Brazil, Wednesday, Feb. 3, 2016. The zika virus is spread by the Aedes aegypti mosquito, which is well-adapted to humans, thrives in people's homes and can breed in even a bottle cap's-worth of stagnant water. The Zika virus is suspected to cause microcephaly in newborn children. |
NEW YORK
(AP) -- A sexually transmitted case of Zika in Texas has scientists
scrambling to understand how much of a risk infection through sex is for
the usually mosquito-spread illness.
Experts
still stress that mosquitoes are the main culprit in the Zika epidemic
menacing Latin America and looming over the United States.
"Mosquitoes
would be the great river of transmission, while sexual transmission is
going to be akin to a mountain stream," said Dr. William Schaffner, an
infectious disease expert at Vanderbilt University.
But
the Texas case has spurred more discussion about additional ways in
which Zika and other illnesses, commonly thought to be carried only by
mosquitoes, might be spread.
Other types of
transmission can be hard to spot in the midst of outbreaks in which many
mosquito-borne infections are occurring, noted Dr. Ali Khan, a former
disease investigator for the U.S. Centers for Disease Control and
Prevention.
"It's very hard to parse this out
in the middle of an epidemic," said Khan, now dean of the University of
Nebraska's college of public health.
Discerning something like sexual transmission would have to occur in a place where an outbreak was not raging, he said.
That's what happened in Dallas.
The
current Zika epidemic is on track to cause millions of infections in
Latin America and the Caribbean, but no transmission was reported in the
United States until the Dallas case this week.
Health
officials said a person there - who had not traveled to an outbreak
area - was infected. An investigation concluded the person caught the
virus through sex with a person who had recently returned from
Venezuela, where Zika infections have been growing.
Officials
released few details about the case, except to say both patients have
recovered. But it wasn't the first to raise the possibility of sexual
transmission of the virus.
A Colorado State
University researcher, Brian Foy, picked up the virus in Africa and
apparently spread it to his wife back home in 2008. More recently, it
was found in one man's semen in Tahiti.
Now,
in the wake of the Dallas case, "we're all kind of scrambling in the
scientific community how best to tackle this and how best to research
it," said Foy.
Most people infected with Zika
experience, at the most, only mild symptoms. But mounting evidence in
Brazil has suggested a connection between the virus and babies born with
brain defects and abnormally small heads.
The
Zika epidemic and possible link to microcephaly cases in Brazil
prompted the World Health Organization to declare a global emergency on
Monday, calling the virus' rapid spread and its apparent link to the
birth defect an "extraordinary event" that poses a threat to the rest of
the world.
WHO spokesman Tarik Jasarevic said Wednesday that the Texas sexual transmission case is "obviously a concern."
"We
need to know more about how likely this is to happen. We also have to
understand whether there are other human-to-human transmission routes,
such as blood transfusion, such as mother-to-child transmission," he
said.
Perhaps a bigger worry than sex is what
dangers may lurk in blood donations from people who have been in Zika
outbreak areas, said Dr. W. Ian Lipkin, a Columbia University infectious
diseases researcher.
"I would raise caution
that any blood used in pregnant women should be tested for the presence
of Zika virus," something that currently doesn't happen, Lipkin said.
The
U.S. Food and Drug Administration says there are no approved tests for
routine screening of blood donations for Zika virus, but it is looking
into the issue. Zika virus usually remains in the blood of an infected
person for a few days but it can be found longer in some people, the CDC
says. This week, the Red Cross said they are asking travelers to Zika
outbreak countries to wait at least 28 days before donating blood.
On
Wednesday, Canadian health officials announced that people who have
travelled outside of Canada, the continental United States and Europe
will be ineligible to give blood for 21 days after their return.
Canadian Blood Services says it is implementing the waiting period to
mitigate the risk of the Zika virus entering the Canadian blood supply.
Meanwhile,
the CDC said it will issue guidance in the coming days on prevention of
sexual transmission of the Zika virus, focusing on the male sexual
partners of women who are or may be pregnant.
It's a tall order, because so much is unknown about sexual transmission and Zika, experts said.
How
long is someone infectious? How long does the virus live in the sperm?
Does it only spread if the first person is suffering symptoms?
Foy said that in his case, he didn't begin to experience symptoms until after he and his wife had sex.
"It's completely black box right now" in terms of how little is known about the risk of sexual transmission, Foy said.
As
worrisome as possible sexual transmission may be, experts stress that
mosquitoes will continue to be the far greater concern. The bugs inject
virus right into the blood stream - an extremely efficient way of
spreading dangerous germs through the body.
"The mosquito is the deadliest animal on the planet," Schaffner said.
