the global eradication effort on the long-term polio years behind and shaken by reverses, got a shot of good news this week. Its leaders said the effort was probably eradicated the second of three varieties of the virus.
The feat, if confirmed, will mark the third time that a separate human pathogen has been erased by vaccination after smallpox and another strain of polio, the scientists write. "This is a very big deal ... that puts us much closer to eradication" of all three poliovirus said Chris Maher, director of the World Health Organization for polio eradication and interventions emergency in the Eastern Mediterranean region, which is not on the new paper. "Two of the three virus [are] down and one to go," he added. the new "auspicious" for the Initiative for global polio eradication (GPEI) accepts Walter Orenstein, an infectious disease specialist at Emory University school of Medicine in Atlanta.
the announcement on November 13 in Morbidity and Mortality Weekly Report ( MMWR ) comes with caveats. The document is entitled "eventual eradication of wild poliovirus type 3-Worldwide, 2012." "Since all the bumps on the road, we try to be careful ... "says Stephen Cochi, co-author and one of the leading scientists on the eradication of poliomyelitis in the uS Centers for Disease Control and Prevention (CDC ) in Atlanta. But "we believe that the evidence is pretty good," said first author Olen Kew, a virologist CDC ensuing whereabouts global virus since 1985.
Poliovirus comes in three varieties, or serotypes, each genetically distinct, with its own personality. Wild-type 2, for example, is more transmissible, whereas wild-type 3 tends to stay put. Wild-type 3 is the "most insidious viruses," Maher said because it causes paralysis in only about one in 1000 people it infects, compared to 0 for 1 wild type and may circulate undetected. The trivalent oral polio vaccine (OPV), which is a horse battle of the campaign is essentially three vaccines in one, and it works best against certain serotypes than others.
Wild-type 2 was the first to disappear worldwide in 1999 although it persists in what is known as a derivative form of the vaccine, created when the attenuated virus used in OPV reverts to its virulent form transmissible. For reasons that are not entirely clear, in most countries that have eradicated polio, wild-type 3 "verified" next to a number of years later, followed closely by wild-types 1, says Kew. In Vietnam, for example, the type 3 disappeared in 1993, and type 1 in 1994. India, the most recent country to eradicate polio, last saw type 3 virus in 2010; Type 1 held just one year. The eradicationists ardently hope the model will generally, and in recent years the GPEI went on a war footing, with more targeted vaccines and an influx of public health workers in infected countries.
The last two wild type 3 observations took place in Nigeria in 2012, where a | 11-month-old was paralyzed in the northern state of Yobe on 10 November. The last positive environmental sample was collected from waste water in Lagos the next day. Despite scouring the DNA evidence of wild poliovirus type 3 since "we can not find anywhere," says Kew. Although encouraged, Orenstein still want intense monitoring year for sure. "In my opinion, it is premature to celebrate the type of eradication 3. "
DATA: WORLD hEALTH thE
CDC scientists say they have made the announcement today because two years of intense surveillance are since the last observation. in addition to investigating stool samples of all cases of acute flaccid paralysis in the world to see if poliovirus is to blame, GPEI now testing environmental samples of wastewater in the footsteps of virus. This "would pick the same case without viruses," Kew said, as happened recently in Israel with wild-type 1 ( Science , November 8, 2013, p. 679).
genetic evidence also points to extinction, says Kew. Wild-type 3 has not disappeared suddenly. "It is not a binary event, you now, now you do not," says Kew. But over the years, the genetic diversity of this serotype decreased from 17 distinct genotypes in 1988 to only two in 2012.
The type 3 disappearance Nigeria adds the encouraging news from this country. He has not seen a trace of wild poliovirus in 3 months and have been only six cases this year. "I'm encouraged we will see a polio-free Africa by the end of the year," said Cochi. "The only uncertainty is persistent Borno, the northeastern state [the terrorist group] Boko Haram is most active."
The MMWR ad can also put even more pressure on the Pakistan, which has a runaway epidemic. the country now represents 85% of all polio cases in the world and constantly re-infect neighboring Afghanistan. with its ballooning housing account more than 235 this year, Pakistan is becoming a global "pariah," Cochi said. If the intensification of the GPEI strategy worked in Nigeria, with its unrest and insecurity, there is no reason it can not work in Pakistan he said, if the government finally gets serious about the eradication of poliomyelitis
* Fix (14 November 2014). in the original map, Guinea been incorrectly labeled as Liberia. the HTML and PDF versions were corrected.
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