Outbreak of wild poliovirus in Namibia

Jun 7 2006

Thirty-four suspect cases with sudden paralysis are under investigation, mostly in the Windhoek area of Namibia, of which three have been confirmed as wild poliovirus.

What is thought to be the first case is a 39-year old man with onset of paralysis on 8 May, later confirmed as infected with wild poliovirus type-1. The majority of suspect cases are over 20 years old; seven of the individuals have died.

National health authorities are planning a response to an outbreak of wild poliovirus in Namibia, polio-free since 1996. An investigation of the outbreak – which unusually appears to be affecting mostly adults – is currently under way. Genetic sequencing confirms that the virus is consistent with an importation from Angola, of Indian origin. Angola, polio-free since 2001, was re-infected last year by a virus from India.

The Government is planning an immunization response consisting of three National Immunization Days (NIDs), using monovalent oral polio vaccine type 1 (mOPV1). The first NID could be conducted as early as 21 June, and will aim to reach the entire population of the country (two million), rather than the usual under-five year population. The age of any further cases will dictate the target age groups for the two subsequent NIDs. An international team is in the country to assist the national authorities.

Namibia began routine immunization for polio in 1990. While the cause of the largely adult outbreak is yet to be determined, it is likely that those who fell ill did not receive immunization as children. Routine immunization coverage within Namibia today varies by region from 60% to 80%.