The primary concern over Zika is its suspected link to
microcephaly, a condition in which a baby is born with an abnormally small
head, which can lead to mental retardation and other complications.The virus has also been linked to Guillain-Barré syndrome, a
rare neurological illness that can cause paralysis.
But questions remain over how Zika is transmitted -- and not
all the answers are entirely conclusive. Here's what we know so far about how
the virus is spread.
Mosquito bites
There is substantial evidence that Zika virus is primarily
spread to humans through the bite of an infected mosquito.
Mosquitoes: "The most murderous animal on Earth"
The Aedes aegypti mosquito -- the species that carries Zika
-- "can bite four or five people in the course of one blood meal, meaning
it can spread disease quickly," CDC Director Dr. Tom Frieden told a
congressional committee earlier this week.
Zika virus has been reported in over two dozen countries,
mostly in Latin America and the Caribbean.
So far in the continental U.S., state and local health
officials report at least 79 travel-acquired cases of Zika virus -- meaning
people who recently visited areas where Zika is actively spreading were
infected there and came back home with the illness.
There have been zero cases of mosquitoes spreading Zika
infection in the U.S. But as the mosquitoes become more prevalent in warmer
weather this spring and summer, that may change.
The Aedes aegypti mosquito is primarily found in southern
states, so as more Zika-infected travelers return home, mosquitoes here could
bite them, pick up the virus, and transmit it to others.
zika-transmission-map-travel-risk-areas.jpg
99 million travelers departed from major Brazilian airports
for international destinations from Sept. 2014 to Aug. 2015. More than 2.7
million of them traveled to the U.S. The circles on this map indicate areas
with greater numbers of travelers from Brazil. Areas shaded in yellow have
mosquitoes that could transmit Zika virus during warmer months, while areas in
orange have them year-round.
The Lancet/CBS News
However, while experts expect there to be some local
transmission in the U.S., they do not anticipate any major outbreaks in this
country.
"If Zika acts like the other types of viruses that are
mosquito-borne that we've had experience with, like dengue and chikungunya, we
will see mini-outbreaks like in Florida and in Texas that can be well
controlled with mosquito vector control. Hopefully we will not see anything
worse than that, but we have to be very vigilant," Dr. Anthony Fauci,
Director of the U.S. National Institutes of Health's National Institute of
Allergy and Infectious Diseases, told "CBS This Morning."
Several factors put the U.S. at an advantage to help keep
Zika at bay, including less dense urban areas than South and Central America,
access to air conditioning and protective screens, and overall better mosquito
control.
Everyone can protect themselves against mosquito bites by wearing
long-sleeved shirts and long pants, staying in places with air conditioning or
that use window and door screens, and using Environmental Protection Agency
(EPA)-registered insect repellents, such as those containing DEET, Picaridin or
a combination.
CDC travel health experts recommend choosing a formula with
at least 20 percent DEET.
Sexual transmission
There have been several instances of sexual transmission of
Zika virus, including a case in Texas earlier this month.
According to Dallas County health officials, a patient there
was infected with Zika after having sexual contact with an ill person who
recently returned from Venezuela, where Zika virus is being spread by
mosquitoes.
The CDC -- drawing on three known cases of sexual
transmission of Zika in the medical research -- reports that the virus may be
present in semen for up to 10 weeks after the onset of illness.
However, it is not known if Zika can persist in semen for
longer than 10 weeks or if infected men who never develop symptoms can transmit
Zika virus to their sex partners.
As such, the CDC recommends that men who live in or have
travelled to a Zika-affected area and have a pregnant partner should abstain
from sexual activity or consistently and correctly use condoms during vaginal,
oral, and anal sex. (Health officials emphasize the importance of protecting
pregnant women because of the risk Zika poses to unborn babies.)
Men who have been in Zika-affected areas should also
consider abstinence or condom use during sexual contact with non-pregnant
partners, the agency advised.
As more research is done on the risk of Zika through sexual
transmission, the CDC is expected to update its guidelines.
Blood transfusions
Earlier this month, Brazilian health officials confirmed two
cases of Zika transmission through blood transfusions from donors who carried
the virus, Reuters reports.
Reporting last week from Recife, the Brazilian town at the
epicenter of the Zika virus outbreak, CBS chief medical correspondent Dr.
Jonathan LaPook noted that many experts think it's a matter of time before all
Brazilian blood transfusions can be tested for the virus.
"We can start to do this, of course," researcher
Rafael Franca told CBS News. "We have the machines, we have the
technology, we have the people to do that. We need to make sure that the test
is going to give solid results."
In the U.S., major blood banks, including the American Red
Cross, have asked people not to donate blood if they've traveled in the last 28
days to Mexico, the Caribbean, South or Central America.
The Red Cross is also asking donors who give blood and
subsequently develop symptoms of Zika virus within 14 days of the donation to
notify the organization so their donated blood can be quarantined.
Other bodily fluids
Scientists have detected evidence that Zika virus can be
found in breast milk, saliva, and urine samples. However, at this time there
have been no reports of transmission in any of these ways, and the CDC has not
issued any cautions about breast feeding or kissing.
"From what we know, and Dr. Anthony Fauci, who's the
head of infectious diseases for the NIH told me, just because you have virus in
the saliva doesn't mean that you can give it to somebody that way," LaPook
said. "I think that's a very important thing.
Sexual transmission
There have been several instances of sexual transmission of
Zika virus, including a case in Texas earlier this month.
According to Dallas County health officials, a patient there
was infected with Zika after having sexual contact with an ill person who
recently returned from Venezuela, where Zika virus is being spread by
mosquitoes.
The CDC -- drawing on three known cases of sexual
transmission of Zika in the medical research -- reports that the virus may be
present in semen for up to 10 weeks after the onset of illness.
However, it is not known if Zika can persist in semen for
longer than 10 weeks or if infected men who never develop symptoms can transmit
Zika virus to their sex partners.
As such, the CDC recommends that men who live in or have
travelled to a Zika-affected area and have a pregnant partner should abstain
from sexual activity or consistently and correctly use condoms during vaginal,
oral, and anal sex. (Health officials emphasize the importance of protecting
pregnant women because of the risk Zika poses to unborn babies.)
Men who have been in Zika-affected areas should also
consider abstinence or condom use during sexual contact with non-pregnant
partners, the agency advised.
As more research is done on the risk of Zika through sexual
transmission, the CDC is expected to update its guidelines.
Blood transfusions
Earlier this month, Brazilian health officials confirmed two
cases of Zika transmission through blood transfusions from donors who carried
the virus, Reuters reports.
Reporting last week from Recife, the Brazilian town at the
epicenter of the Zika virus outbreak, CBS chief medical correspondent Dr.
Jonathan LaPook noted that many experts think it's a matter of time before all
Brazilian blood transfusions can be tested for the virus.
"We can start to do this, of course," researcher
Rafael Franca told CBS News. "We have the machines, we have the
technology, we have the people to do that. We need to make sure that the test
is going to give solid results."
In the U.S., major blood banks, including the American Red
Cross, have asked people not to donate blood if they've traveled in the last 28
days to Mexico, the Caribbean, South or Central America.
The Red Cross is also asking donors who give blood and
subsequently develop symptoms of Zika virus within 14 days of the donation to
notify the organization so their donated blood can be quarantined.
Other bodily fluids
Scientists have detected evidence that Zika virus can be
found in breast milk, saliva, and urine samples. However, at this time there
have been no reports of transmission in any of these ways, and the CDC has not
issued any cautions about breast feeding or kissing.
"From what we know, and Dr. Anthony Fauci, who's the
head of infectious diseases for the NIH told me, just because you have virus in
the saliva doesn't mean that you can give it to somebody that way," LaPook
said. "I think that's a very important thing
By.Dr. Jessica Shepherd
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