Polio in Three New African Countries: Zambia, Chad, and Togo

The World Health Organization (WHO) reported three new countries that recently reported cases of circulating vaccine-derived polio virus type 2 (cVDPV2) cases.

Zambia

According to the Ministry of Health of Zambia, a 2-year-old case of cVDPV2 was reported in Chienge district, Luapula province, bordering the Democratic Republic of Congo. This is the first case reported since 1995.

Chad

A case of cVDPV2 was reported in a 13-month old child. The case was reported from Chari Baguirmi province, bordering Cameroon. The last polio case reported in Chad was in 2000.

Togo

A case of cVDPV2 was reported in a 30-month old child from Plateaux province, bordering Benin and Ghana. The last polio case reported in Togo was in 1999.

Advice

These patients are not infected with the wild polio virus. A potential, but rare, adverse effect of the oral polio vaccine (OPV) is the ability to recombine to a form that may cause neurological infection and paralysis. This is believed to be a rare event, but outbreaks of vaccine-associated paralytic poliomyelitis, caused by a circulating vaccine-derived poliovirus (VDPV), have been reported. Circulating VDPVs occur when routine or supplementary immunization activities are poorly conducted and a population is left susceptible to poliovirus, whether from vaccine-derived or wild poliovirus. Hence, the problem is not with the vaccine itself, but low vaccination coverage. Outbreaks of paralysis due to the vaccine derived strain tend to occur in areas where polio vaccination levels have not been maintained in the general population.

Travellers to any country that reports cases of polio (whether wild or vaccine-derived type) can reduce their risk of exposure to poliovirus by ensuring that their childhood vaccinations, including polio, are up-to-date prior to travelling. For added protection, travellers who are visiting countries where transmission of the polio virus is continuing should receive an additional dose of oral polio vaccine or inactivated polio vaccine within 4 weeks to 12 months before travelling.