RPT-Zika virus may hide in organs protected from the immune system – Reuters

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(Repeats story published Friday with no changes)

By Julie Steenhuysen

CHICAGO Feb 14 The Zika virus may be
particularly adept at entrenching itself in parts of the body
that are shielded from the immune system, making it harder to
fight off and possibly lengthening the timeframe in which it can
be transmitted, top U.S. experts said on Friday.

Researchers reported that Zika virus can be detected in
semen for 62 days after a person is infected, adding to evidence
of the virus’s presence in fetal brain tissue, placenta and
amniotic fluid. Their work is part of an international race to
understand the risks associated with Zika, a rapidly spreading
mosquito-borne virus thought to be linked to thousands of cases
of birth defects in Brazil.

“Right now, we know it’s in the blood for a very limited
period of time, measured in a week to at most 10 days. We know
now, as we accumulate experience, it can be seen in the seminal
fluid. We’re not exactly sure after the infection clears, where
else it would be,” Dr. Anthony Fauci, director of the National
Institute of Allergy and Infectious Diseases said.

“These are all things that need to be carefully examined in
natural history and case-control studies,” he said.

Fauci said that Zika’s persistence in the body recalled
findings during the 2014 Ebola outbreak, the worst on record. In
individual patients, the highly deadly virus remained in semen
and eye fluid for months.

Zika causes only mild symptoms, and in most cases may not
result in illness at all. Its suspected link to the birth defect
microcephaly and to neurological disorder Guillain-Barre
syndrome has generated alarm among public health officials,
though an association has not been proven. The World Health
Organization on Feb. 1 declared Zika a global health emergency.

Several organs in the body, including the testes, the eyes,
the placenta and the brain, are “immune privileged” – protected
from attacks launched by the immune system to neutralize foreign

These sites are safeguarded from antibodies to prevent the
immune system from attacking vital tissues. But if a virus
enters these protected sites, it is much harder to fight them

“The virus can continue to persist and or multiply,” said
Dr. William Schaffner, an infectious disease expert at
Vanderbilt University Medical Center in Nashville. “The virus is
in a bubble of sorts.”

Fauci said it is not entirely surprising that Zika persists
in semen. There have already been at least two reports in which
the virus was likely transmitted sexually. What has not been
clear is for how long.

British researchers offered some clues on Friday. In a
letter to the journal Emerging Infectious Diseases, scientists
reported the case of a 68-year-old man who was infected with
Zika in 2014. They detected Zika virus 62 days after the initial
infection, but they were not able to confirm whether it could
still infect another person.

Earlier this week, researchers in Slovenia published a paper
in the New England Journal of Medicine describing a severely
brain damaged fetus from a mother who was infected with Zika in
Brazil and later terminated the pregnancy.

In an autopsy, the authors found high levels of Zika in the
brain and some evidence that the virus had been replicating.
They suggested that Zika may persist in the fetal brain because
it is an immunologically privileged site.

That is true of many other viruses, such as toxoplasmosis,
rubella, cytomegalovirus or herpes, which can also cross the
placenta and cause microcephaly, a birth defect marked by small
head size and underdeveloped brains. Doctors commonly screen
pregnant women for these infections, said Dr. Ian Lipkin of the
Center for Infection and Immunity at Columbia University in New

Lipkin said the key concern about Zika harboring in immune
protected sites is that it could be transmitted sexually through

So far, there is little to suggest sexual transmission is
common, said Dr. Eric Rubin, an infectious disease expert at the
Harvard School of Public Health, “but it will bear looking at so
that we can counsel individuals about the risk that they pose to

U.S. health officials advise that men who come to the
country from Zika outbreak areas should consider using condoms
even with nonpregnant sex partners because the virus may persist
in semen even after it clears the bloodstream.

“They don’t say for how long,” Schaffner said. “That’s
because they don’t know. As it was with Ebola, we’re learning as
we go.”

(Reporting by Julie Steenhuysen; Editing by Michele Gershberg
and Lisa Shumaker)

RPT-Zika virus may hide in organs protected from the immune system – Reuters