Polio Outbreak in China
China — the country with the world’s largest population — was certified as poliomyelitis-free in 2000. A decade later, a poliomyelitis outbreak occurred in the province of Xinjiang. In response, the Chinese CDC initiated an investigation and a massive vaccination campaign.
In the investigation, poliomyelitis cases were defined as acute flaccid paralysis in children aged <15 years or paralytic illness in any person if poliomyelitis was suspected. Cases were considered laboratory-confirmed if wild-type virus was detected in stool samples, and clinically compatible if there was no stool confirmation of wild-type virus.
The index patient — a 16-month-old girl whose family had no history of travel outside Xinjiang — developed paralysis on July 3, 2011. By October 9, 2011, 44 cases (21 laboratory-confirmed and 23 clinically compatible) had been identified. Incidence was highest among children aged <1 year and was higher in males than in females. Sequence analysis performed on isolates from the index patient and three other patients implicated an imported wild-type virus that originated in Pakistan.
A “level 2” public health emergency response, the highest level that the China Ministry of Health was authorized to initiate, was launched. Between August 2011 (4 weeks after confirmation of the outbreak) and April 2012, 43.7 million doses of oral polio vaccine were administered in the province. The outbreak was stopped within 1.5 months after laboratory confirmation of the index case.