A new virus related to the one that caused SARS a decade ago was
reported in an 11th person this week, spurring scientists to find
the source of the lethal germ.
The latest case, identified in the U.K., was probably the result
of human
to human transmission and increases the need for countries
to watch for unusual patterns of respiratory disease, the World
Health Organization said yesterday.
The infected person hadn’t traveled recently and is related to a
person whose infection was announced Monday.
The source of the pathogen, a coronavirus that emerged as recently
as April, hasn’t yet been discovered, frustrating efforts to curb
its spread. Cases in humans provide opportunities for the virus to
mutate and become more easily transmissible among people,
potentially setting off a pandemic like the Severe Acute
Respiratory Syndrome that sickened more than 8,000 people, killing
774, in 2002 and 2003.
“The low number spread over a long period suggests that sporadic
jumping from animals to human is the most likely explanation,”
said Yuen
Kwok-yung, chairman of infectious diseases at the University of
Hong Kong’s department of microbiology.
Previous cases were reported in Saudi Arabia, in areas around
Jeddah and Riyadh, and in Jordan and Qatar. Genetic evidence
indicates the virus is most closely related to a coronavirus found
in bats, the WHO said in November.
That link suggests that bats would be “the most likely wildlife
reservoir,” said John
Mackenzie, a Melbourne-based virologist who helped investigate
SARS as leader of a WHO delegation to China. “Challenges exist
about gaining the wildlife samples to explore which might be
carrying the virus,” he said.
“It’s important to know the source so at least you have some
indication of what the risks are and to what extent that risk
exists,” said Mackenzie, who is an honorary professor of
microbiology at the University of Queensland. “The evidence now
suggests that the chances of an outbreak like SARS is unlikely - -
it doesn’t seem to transmit that readily.”
Of the 11 confirmed cases of human infection notified to the WHO
since April 2012, five have been fatal. The latest case is being
treated in an intensive care unit, the Geneva-based agency said in
a statement yesterday.
Undetected Cases?
“The fact there are still new cases occurring is a concern because
pathogens can change and emerge genetically to become more
transmissible over time,” said Raina
MacIntyre, professor of infectious diseases epidemiology at
the University of New South Wales.
“If human-to-human transmission is occurring, another possible
explanation could be that there are many more undetected
cases.”
Screening blood tests have found no signs of existing or previous
infections among the general population in Saudi Arabia, Yuen said,
citing informal information available on the Internet.
“This again suggests that the virus is not transmitted at a low
level in the human population, but that a new viral infection
recently entered the human population,” he said in an e-mail
today.
Coronaviruses encompass a family of germs that cause illnesses
ranging from the common cold to SARS, which was far more
transmissible than the new virus currently appears, according to
the WHO.
The Geneva-based United Nations agency recommends clusters of
severe acute respiratory infections, especially in health- care
workers, be thoroughly investigated, regardless of where in the
world they occur, it said yesterday.
“This new development does justify the measures that were
immediately put into place to prevent any further spread of
infection and to identify and follow up contacts of known cases,”
said John Watson, head of the U.K.’s Health Protection Agency’s
respiratory diseases department, in a statement yesterday.
“To date, evidence of person-to-person transmission has been
limited,” Watson said. “Although this case provides strong evidence
for person to person transmission, the risk of infection in most
circumstances is still considered to be very low.”
The emergence of the new pathogen shows why outbreak surveillance,
notification and response systems can’t be “disease-specific,”
said William
Aldis, an assistant professor of global health at Bangkok’s
Thammasat University and a former WHO representative to
Thailand.
“Otherwise we will forever be looking for the last infectious agent
or vector, not the next one,” Aldis said in an e-mail. “We need to
support outbreak surveillance and response systems coherently, not
disease-by-disease.”
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