Friday, May 28, 2010

PRRS - viet nam (04): Human Infection Debated


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A ProMED-mail post
<http://www.promedmail.org>
ProMED-mail is a program of the
International Society for Infectious Diseases
<http://www.isid.org>

Date: Fri 28 May 2010
From: Trevor Drew <t.w.drew@vla.defra.gsi.gov.uk> [edited]


Re: ProMED-mail Porcine reprod. & resp. syndrome - Viet Nam (02),
human fatality suspected 20100526.1751
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I would like to endorse the views expressed by Dr Kelly Lager
(ProMED-mail posting no. 20100527.1762), concerning the supposed
involvement of PRRSV in human deaths in Viet Nam. As a pig virologist
who has spent many years studying this virus, both in Europe and in
Asia, I am also concerned about the claims made by a Vietnamese
medical official, that PRRSV was causative in this and other cases in
that country. There has been no accompanying scientific evidence to
support such a claim and, without such evidence, these claims only
serve to generate significant disruption and possibly panic within
the population of Viet Nam and beyond. Also, quite apart from the
potential damage to the larger-scale pig production in the region,
pigs are a significant part of the rural economy and a major protein
source for the country - constituting more than 70 percent of the
total meat production of the region.

Pigs are also part of the societal fabric, often acting as a form of
savings and additional income at times of hardship, school fees, etc.
So any associated panic could have significant sociological
consequences in the longer term. As Kelly Larger says, there are far
more reasonable explanations for this small number of deaths.

Anyone who has been studying this virus must be concerned about the
increasing diversity exhibited by this virus, particularly in Asia,
where the methods of production and numbers of pigs seem to provide
optimal conditions for its evolution.
And, considering PRRSV is a
virus relatively new to pigs, having been known to science only for
the last 20 years, it would be rash to totally dismiss the
possibility of a jump to another species, including man. But until
this and other cases are carefully investigated, I would suggest it
is the duty of all scientists and communicators of science to present
such information in a responsible way.

I raise the question of whether the inclusion of the caveat within
the initial and subsequent ProMED reports was sufficient, or whether
the opinion of a PRRSV expert should have been sought and published
alongside the original report.

--
Prof Trevor Drew PhD, MSc, CBiol, MSB
Head of Virology Department
Head of Statutory and Exotic Virus Programme
Chair, VLA Academic Board
OIE Reference Expert for CSF, BVD & EVA
Veterinary Laboratories Agency (Weybridge)
New Haw, Addlestone
Surrey KT15 3NB
UK
<t.w.drew@vla.defra.gsi.gov.uk>
<http://www.vla.gov.uk/>

[Editor's comment: We appreciate Prof. Drew's views as an expert on
this topic and thank him for this contribution. ProMED sees its
primary role as a provider of early warnings of emerging disease
outbreaks. Thus we need to balance the requirement for rapid
reporting, needed to recognize and combat an outbreak, with the need
for cautious interpretation of incomplete information and
deliberation among experts. We decided to pass along this news story
(which was already widely available on the Internet and in the public
domain) with our view that the occurrence of PRRS in humans was
unproven and indeed unlikely. Part of our role is to temper media
sensationalism with rational context.

As Prof. Drew states however, species jumps can and do occur
unexpectedly. Such species jumps are an important source of newly
emerging infectious diseases and a major reason for ProMED's emphasis
on "one medicine" in our reporting. We also recognize our obligation
to provide a forum for informed discussion and to present further
evidence, which we eagerly await, as it becomes available. - Ed.LM]

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