Last week, the Indian government issued a directive to urgently immunize 300’000 children between the ages of six weeks and three years in Hyderabad, Telangana, following the discovery of an active strain of poliovirus. The pathogen was detected in a sewage sample taken near Hyderabad’s Secunderabad railway station and confirmed by the Ministry of Health to be of a type 2 strain. The type 2 strain has been almost completely eradicated world-wide with the last recorded incident in 1999 from Aligarh, India. The Ministry also stated that there is little concern as no children within a radius of several kilometres from the source were found to be affected.
India’s eradication of polio has been a major public health achievement with the last case registered on the 13th of January 2011. In March of 2014, the World Health Organisation (WHO) classified India as being a polio free nation after a twenty year struggle and the equivalent of millions of dollars invested in an effort that has made the country free of the disease.
Poliomyelitis, commonly called polio is a highly infectious disease caused by the poliovirus that multiplies in the intestine and attacks the nervous system resulting in paralysis within a matter of hours if left untreated. The poliovirus usually spreads from human to human following the faecal-oral rout, or less commonly the oral-oral pathway. There is currently no cure against polio but prevention methods have proven to be effective with the use of bivalent, and later on trivalent oral vaccines called Oral Polio Vaccine (OPV) in the form of a liquid.
According to the regional health officer for the northern Indian city of Allahabad Dr. Rajesh Singh, the emergence of the virus may have been caused by the OPV itself. As a high number of children have been vaccinated, the dissolved liquid then passes through stool and accumulates in sewage areas. Overtime, this might have made the poliovirus more resistant.
This method of infection called vaccine derived polio virus (VDPV) remains a global health issue although these outbreaks are extremely localised and generate a prompt response from health authorities. In order to avoid the spread of VDPV’s, the Global Polio Eradication Initiative, a public-private partnership led by national governments and headed by the WHO, Rotary International, the US Centre for Disease Control and Prevention (CDC), and the United Nations Children’s Fund (UNICEF) recommends to switch from the trivalent OPV, which contains type 1, 2 and 3 serotypes to the bivalent vaccine containing only serotype 1 and 3. This strategy started implementation in April of this year. In order to complete the eradication of the virus and the risk of vaccine derived polio, the Global Polio Eradication Initiative aims to phase out the use of OPV’s world-wide by the year 2019-2020.