- The Ebola virus, which has caused deaths from high fever
and bleeding in African outbreaks, can also infect without producing illness,
according to a new finding by African and European scientists.
- The possibility of asymptomatic infection was only suggested
in earlier studies, they said in last week's issue of The Lancet, a medical
journal published in London. Now they said they had documented such infections
for the first time. They found that the Ebola virus could persist in the
blood of asymptomatic infected individuals for two weeks after they were
first exposed to an infected individual. How much longer the virus can
persist is unknown.
- All outbreaks of Ebola have been controlled by standard
infection control measures such as effective body disposal, destroying
or sterilizing contaminated equipment and appropriate use of gloves. But
if people can be carriers without showing symptoms, it means control might
be more difficult.
- "This degree of containment would be virtually impossible
if symptom-free carriers posed a significant threat of infection,"
Dr. Alan G. Baxter of Newtown, Australia, wrote in an editorial in the
same issue of The Lancet.
- Scientists have known that Ebola usually spreads from
an infected person to another individual and through contamination in clinics
or hospitals. The new finding suggests that some cases may result from
healthy carriers. How often is unknown. The finding could help scientists
in their long-term quest to develop effective therapies to treat the virus
or perhaps even a vaccine to prevent infection.
- But an immediate effect is to raise the need to reasses
health policy about one of the most virulent viruses known and to determine
how often healthy carriers transmit it, said the scientific team headed
by Dr. E. M. Leroy of Franceville, Gabon.
- One concern is transmitting Ebola through blood transfusions.
Dr. Thomas G. Ksiazek, an expert in Ebola at the Centers for Disease Control
and Prevention, a federal agency in Atlanta, said that such concern would
be much greater in Africa than in the United States, where blood banks
usually ask people who have been in Africa in recent months not to donate
because of the threat of transmitting malaria.
- Dr. Leroy's team said another public health concern was
transmission of Ebola virus from healthy carriers through sex. Other scientists
have detected Ebola in semen.
- About 70 percent of people with symptoms of Ebola have
died in widely publicized outbreaks in the central African countries of
Gabon, the Democratic Republic of the Congo and Sudan.
- Illness often begins abruptly, from 5 to 10 days after
exposure to Ebola virus, with symptoms like fever, headache, vomiting and
diarrhea. Then bleeding can occur internally or ooze from needle sites
and through the nose and mouth. Death usually occurs from five to seven
days after the onset of illness.
- Dr. Leroy's team studied 25 individuals who never developed
symptoms although they lived with family members and cared for them without
using gloves and other precautions in two outbreaks in Gabon in 1996.
- Using standard virologic techniques, the scientists from
Gabon, Germany and France said they could not detect the virus in the blood
of the healthy contacts. But Dr. Leroy's succeeded by using a technique
known as polymerase chain reaction to grow the tiny amount of virus present.
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