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Health scare as researchers find traces of polio virus in Eastleigh

The government is on a high alert after experts from the Kenya Medical Research Institute (Kemri) and Centres for Disease Control and Prevention (CDC) reported finding traces of a vaccine-derived polio virus in environmental samples from Eastleigh, Nairobi.

In a statement to county directors of health, the Director of Medical Services, Dr Jackson Kioko, warned that the circulating vaccine-derived polio virus type 2, could cause paralysis in un-immunised people.

“In view of this confirmation, the ministry wishes to put all the healthcare workers on alert for a potential outbreak by this type of virus,” said Dr Kioko.

“Genetic sequencing of the isolate in CDC Atlanta laboratories subsequently confirmed it is circulating vaccine-derived polio type 2 (CVDPV2),” reads the alert to county directors of health.


This development means it might take longer for the World Health Organisation (WHO) to certify the country as polio-free. The WHO no longer considers a country polio-free until 12 months have passed without a case – or a positive environmental sample.

“A vaccination campaign will be conducted in Nairobi County from May 5 to 9. Subsequent campaigns will include other high-risk counties,” Dr Kioko said.

Polio is an infectious disease caused by the poliovirus and is transmitted through contaminated water or food, or contact with an infected person.

Many people infected with the poliovirus neither fall sick nor have any symptoms. However, those who do become ill develop paralysis, which can be fatal.

A vaccine-derived poliovirus is a rare type of polio virus that has genetically mutated from the live, weakened strain contained in the oral polio vaccine.


A day or two after children are given polio drops, the weakened virus in the vaccine is shed in stool.

In areas of poor sanitation, the excreted vaccine-virus can spread to the immediate community (to protect other children through ‘passive’ immunisation), before eventually dying out.

Kenya established environmental sample surveillance in 2013, following an outbreak in Somalia, which saw 14 cases imported in the country.

Nine sites in Nairobi, Garissa, Mombasa and Kisumu counties are involved in surveillance.