The total number of polio cases worldwide declined by 34 percent last year, from 1,997 cases in 2006 to 1,310 in 2007, according to the May 9 Morbidity and Mortality Weekly Report. The international eradication program’s focus on the more-virulent type 1 virus (WPV) has paid off, but type 3 (WPV3) experienced a significant upsurge.
India had the most total cases in 2007, with 870. Increased use of monovalent type 1 vaccine led to a dramatic 87 percent decline in WPV1 cases, from 646 in 2006 to 83 in 2007. Transmission of this strain may be interrupted in 2008. On the other hand, an outbreak of WPV3 drove the number of WPV3 cases up from just 28 in 2006 to 787 last year.
Nigeria cut its total case count from 1122 in 2006 to 285 last year. WPV1 cases were down 86 percent and WPV3 cases were down 39 percent. However, there has been a worrying increase in WPV1 cases so far this year. Problems with the quality of vaccination campaigns have been reported, and large numbers of children still go unvaccinated.
Cases in the other two endemic countries, Pakistan and Afghanistan, also declined slightly last year, as reported in last month’s IDSA News.
Polio cases continued to crop up in six of the 13 formerly polio-free countries that had imported WPV cases in 2006. In addition, Burma (11 cases) and Sudan (one case) had their first outbreaks in several years.
Widespread use of monovalent type 1 vaccine will continue, and efforts to improve campaign quality are ongoing.
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