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]

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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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