Highlights 

• The polio endgame is proving to be challenging. On June 29, 28 children in the Democratic Republic of the Congo (DRC) were paralysed by the circulating vaccine-derived polio virus Type 2 (cVDPV).
• The World Health Organisation (WHO) has assessed the overall public health risk at the “national level to be very high and the risk of international spread to be high”.
• The outbreak, first reported from Haut-Lomami Province in June 2017, has since spread to five more provinces, the latest being Ituri Province this May. Since this province is close to Uganda, there is a heightened risk of the virus spreading within and outside Africa. According to the WHO, there is an increased risk of virus transmission during the imminent rainy season.
• Adding to the complexity has been the detection of three different cVDPV2 outbreaks in the DRC. While the first Type 2 vaccine-derived strain (from Haut-Lomami Province) has spread to three provinces, two other Type 2 strains have been detected from two other provinces.
• Because of intensified immunisation using oral polio vaccination (OPV), polio cases caused by the wild virus have reduced by 99.9% since 1988. However, as live, weakened viruses are used in OPV, there is a remote possibility of the virus turning virulent and causing vaccine-derived polio virus outbreaks. This is best seen in the case of Type 2 polio virus.

The only way to stop the outbreaks is by using OPV containing only Type 2. While the renewed use of Type 2 OPV raises the risk of further shedding of Type 2 viruses, using the polio vaccine injection (which uses only killed viruses) is not recommended during an outbreak as it takes longer to protect vaccinated children.

Source: The Hindu