Seals pose influenza threat

[Guest guest]

INFLUENZA B, SEALS - NETHERLANDS

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Date: 12 May 2000

Source: BBC News 12 May 00 [edited]

Seals pose influenza threat

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The influenza B virus has been found in animals for the first time, with

the scientists who made the discovery saying it " may pose a direct

threat

to humans " . The virus was found in up to 2 percent of seals on the Dutch

coast in 1999 and was identical to the virus prevalent in humans in the

Netherlands in 1995.

The virus is being harbored unchanged by the seal. Since the human

immune

response to a particular virus strain fades with time, any later

reintroduction of that strain might have a serious impact.

According to team leader Professor Albert Osterhaus, from the National

Influenza Center at Erasmus University, " My message is if you find these

animals at the beach, just don't touch them. Stay away and wait until a

professional comes. "

There are 3 types of influenza virus, A, B and C. The A type is harbored

in

birds and also infects humans. It has been responsible for the last

century's major pandemics. Until now, the B type was thought to be an

exclusively human disease.

Dr Alan Hay, Head of the WHO Influenza Center at the UK National

Institute

for Medical Research said: " The idea of an animal reservoir would be

controversial. " Animal reservoirs are important because they harbor the

viruses, allowing infections to resurface after quiet periods. They can

allow viruses to mutate and become more virulent.

This had not happened in the Dutch seals. The virus had remained the

same

for 4 years. But the human virus, and the human immune response, changes

every year. If the old virus resurfaced at a later date, it could be

much

more potent than the annual human virus because, in effect, people's

bodies

had " forgotten " it.

Professor Albert Osterhaus said: " The virus is in an evolutionary

stasis,

apparently for 5 years. If this continued for another 5 or 10 years and

then it came back into the human population, then the immunity may have

dwindled. That's an interesting thing to realize.

" The [influenza] B virus is not a mild virus. For example, in the

Netherlands more people die of flu than in road accidents. These flu

deaths

are caused by B viruses. These are dangerous viruses. "

However, Dr Hay noted: " One of the major requirements for infection is

close contact and we don't go around kissing seals, do we? "

In 1999, the Dutch scientists found 12 seal pups with breathing

difficulties, stranded on the coast. They took the seal pups to the Seal

Rehabilitation and Research Center in Pieterburen and tested them for

viruses. Surprisingly they found influenza B and are confident they have

ruled out the possibility of laboratory contamination. They then tested

971

stored blood samples, taken from seals admitted to the center since the

1980s. Before 1995, none of the 580 samples contained influenza B. But

from

1995 onwards 2 percent of the 391 samples showed evidence of the virus.

This [these] data, and the fact the virus was a 1995 strain, shows the

seals caught a human virus in 1995.

Professor Osterhaus thought it unlikely the infection occurred in a

rehabilitation center as workers wear protective clothes and take other

precautions: " I think its much more likely someone found a seal stranded

on

a beach and accidentally coughed into its face. " The research is

published

in the journal Science.

--

M. Cosgriff

mcosgriff@...

[seal-to-human transmission of influenza A virus has been reported

(Webster

RG, JR Geraci, G Petursson and K Skirnisson. Conjunctivitis in humans

exposed to seals infected with an influenza A virus. NEJM 304:911, 1981)

and this new report extends the host range (and reservoir) of influenza

B

to include pinnipedia.

The original article discussed above is A.D.M.E. Osterhaus, G.F.

Rimmelzwaan, B.E.E. a, T.M. Bestebroer, and R.A.M. Fouchier.

Influenza B virus in seals. Science May 12 2000: 1051-1053. - Man. Ed.

DS]

.........................tg/ds