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Poliomyelitis Outbreak Spreads Across Yemen: Case Confirmed in Indonesia

On 29 April 2005, 18 new cases of polio were confirmed in Yemen, bringing the reported total number associated with the outbreak in the country to 22. Prior to this outbreak, Yemen had never detected a wild poliovirus since acute flaccid paralysis (AFP) surveillance began in 1996. Laboratory investigation has confirmed that the virus responsible for the Yemen outbreak is very closely genetically related to wirld poliovirus currently circulating in Sudan.

The first indication of the outbreak was the confirmation of four polio cases on 20 April 2005 in Hudeida governorate, in the south-western part of the country on the Red Sea coast. The latest 18 cases were reported from five governorates, including the country's capital Sana'a. Ongoing field investigations have identified additional AFP cases in the affected governorates – these cases are currently being investigated.

Teams of Ministry of Health and the World Health Organization (WHO) epidemiologists are investigating the outbreak and planning for an appropriate immunication response – the immunication response will be nationwide. It is planned to use the recently developed monovalent oral polio vaccine type 1 (mOPV1). This new vaccine enables a precisely tailored immunological response to the type poliovirus that is causing the outbreak. Compared with the commonly used trivalent OPV, which offers protection against all three types of wild poliovirus, mOPV1 provides a greater immunity to type 1 wild poliovirus with fewer doses. Yemen had already conducted one national immunization round from 11 to 14 April 2005 prior to confirmation of the outbreak, as the country was considered to be at high risk of importation of wild poliovirus from nearby Sudan, where an outbreak of polio is continuing.

On 21 April 2005, wild poliovirus type 1 was detected and reported by the national polio laboratory in Bandung, Indonesia. On 2 May 2005, this result was confirmed by the global reference laboratory in Mumbai, India. The case, an 18 month-old child from Sukabumi district, West Java, had onset of paralysis on 13 March 2005. The Ministry of Health of Indonesia, supported by WHO, immediately initiated a detailed investigation in the district and surrounding areas, as well as an outbreak response immunization in the immediate surroundings of the case. Additional AFP cases have been identified and are under investigation. The findings of the recent investigation suggest recent introduction of wild poliovirus: genetic analysis of the virus demonstrates that its origin is in west Africa, similar to the viruses which cased an outbreak in 2003-2004 in that region. Further analysis suggests the virus travelled to Indonesia through Sudan, and is similar to recently isolated viruses in Saudi Arabia and Yemen. Indonesia had been polio-free since 1995. The Ministry of Health of Indonesia is also planning a wide-scale immunization response.

Experience in polio demonstrates that outbreaks can be quickly contained with high-quality immunization campaigns which reach every child aged < 5 years. Global eradication efforts have reduced the number of polio cases from 350,000 annually in 1988 to 1,267 cases in 2004. Six countries remain polio-endemic, with a further six where polio transmission has been reestablished.

Further information is available at www.polioeradication.org.

Source: WHO Weekly Epidemiological Record, Vol 80, No. 18, 2005.