J Infect Dis. 2004 Apr 1;189(7):1168-75. Epub 2004 Mar 16.
Related Articles,
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Isolation and characterization of circulating type 1 vaccine-derived
poliovirus from sewage and stream waters in hispaniola.
Vinje J, Gregoricus N, Martin J, Gary HE Jr, Caceres VM, Venczel L, Macadam
A, Dobbins JG, Burns C, Wait D, Ko G, Landaverde M, Kew O, Sobsey MD.
Department of Environmental Sciences and Engineering, School of Public
Health, University of North Carolina, Chapel Hill, North Carolina, USA.
janvinje@email.unc.edu.
Twenty-one cases of acute flaccid paralysis (AFP) were reported on the island
of Hispaniola in 2000. Laboratory analysis confirmed the presence of
circulating vaccine-derived poliovirus (cVDPV) type 1 in stool samples
obtained from patients. As a complement to the active search for cases of AFP,
environmental sampling was conducted during November and December 2000, to
test for cVDPV in
sewage, streams, canals, and public latrines. Fifty-five environmental
samples were obtained and analyzed for the presence of polioviruses by use of
cell culture followed by neutralization and reverse-transcription polymerase
chain reaction. Of the 23 positive samples, 10 tested positive for poliovirus
type 1, 7 tested positive for poliovirus type 2, 5 tested positive for
poliovirus type 3, and 1 tested positive for both poliovirus type 2 and type
3. By sequence analysis of the complete viral capsid gene 1 (VP1), a
2.1%-3.7% genetic sequence difference between 7 type 1 strains and Sabin type
1 vaccine strain was found. Phylogenetic analysis showed that these viruses
are highly related to cVDPV isolated from clinical cases and form distinct
subclusters related to geographic region. Our findings demonstrate a useful
role for environmental surveillance of neurovirulent polioviruses in the
overall polio eradication program.
PMID: 15031784 [PubMed - in process]

http://seattletimes.nwsource.com/html/nationworld/2004092236_polio26.html?syndication=rss
Wednesday, December 26, 2007 - Page updated at 12:00 AM
Polio eradication is still a struggle
By David Brown
The Washington Post
· Archive | Polio fight gets $200 million from Gates, Rotary foundations
WASHINGTON — The troubled 19-year-old campaign to eradicate polio is celebrating
recent progress and an unexpected infusion of cash, but experts realize they
will not be able to end the expensive and laborious efforts to control the virus
any time soon.
Ridding the world of polio will be a far messier business than the 1977
eradication of smallpox, which remains a unique achievement in medicine. That is
because it is clear the virus that causes polio could re-emerge years, possibly
decades, after the last case is found.
The reason involves peculiarities of poliovirus and the oral (Sabin) vaccine
being used to eradicate the disease.
The vaccine contains a weakened poliovirus that stimulates immunity against the
"wild" virus, which can cause paralysis. On rare occasions, however, the vaccine
virus can mutate to a more dangerous form, spread from person to person and
cause a paralytic infection.
This phenomenon, only recognized in the past decade, has caused outbreaks in 10
countries since 2000. This year, 7 percent of all polio cases worldwide were
caused by mutant, vaccine-derived virus.
The only way to prevent this is to keep the world's infants and toddlers fully
immunized, in other words, to keep up the expensive full-court press that has
gone on seven years longer than anticipated.
To rid the planet of polio, people eventually will have to stop using the oral
vaccine. Whether they should forgo immunization altogether or use the
alternative vaccine — the Salk "polio shot" that does not contain live virus and
cannot cause infection — is under debate.
Switching to the Salk vaccine, however, will be hard.
It's more expensive: roughly $2.70 a dose, compared with 15 cents for the oral
vaccine. About 135 million infants are born each year, and each will need at
least two shots. While the two companies that make most of the world's supply
can ramp up production, it will take them at least five years, possibly a lot
longer.
Consequently, even after eradication, many countries will have to continue using
the oral vaccine — and be prepared to play a global version of whack-a-mole,
spotting and suppressing mini-epidemics caused by it.
This all adds up to an outcome nobody anticipated in 1988, when the World Health
Organization (WHO), emboldened by the smallpox success, took on polio.
"My major concern has been that the eradication of wild virus may not be the
whole problem in terms of eliminating the disease, or even protecting the world
from it," said Ellie Ehrenfeld, a virologist at the National Institutes of
Health and an adviser to WHO.
Saving lives, money
Before the eradication campaign began, polio paralyzed more than 350,000 people
a year in 125 countries. Stopping that is the chief goal of eradication.
But health officials also hoped the end of polio would mean the end of polio
vaccination, with its trouble and expense. That was the case with smallpox. No
country routinely vaccinates against that disease anymore, a move that has saved
more than $17 billion in the United States alone.
But an unambiguous transition to a "polio-free" world is unlikely. It will be
hard to know when, if ever, it will be safe to forgo vaccination.
Part of the reason is a fear that terrorists might intentionally reintroduce the
virus, a possibility countries did not worry about much when they decided to
stop smallpox vaccination. But there is also the chance of accidental or
unrecognized release.
Work is under way to identify laboratories holding poliovirus, reduce their
number and increase their security. But unlike with smallpox, there may be
places that have the pathogen but do not know it.
Poliovirus replicates in the intestine. Thousands of labs around the world have
frozen samples of feces that may contain the virus — either the wild type or the
vaccine virus — that could theoretically escape.
Further complicating matters is the fact that most polio cases are "silent." In
only 1 in 200 infections from the wild virus is there the characteristic muscle
weakness that lets physicians make the diagnosis. Polio virus can travel far
before anyone knows it.
"There is going to be a period — and perhaps indefinitely — where the world is
going to want that umbrella of protection," said Stephen Cochi, a physician at
the U.S. Centers for Disease Control and Prevention (CDC) who chairs a committee
advising WHO on polio eradication.
Polio caused by vaccine-derived virus is only one of the obstacles recently
encountered by the Global Polio Eradication Initiative.
Copyright © 2007 The Seattle Times Company
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