Afghanistan: Increased activity for circulating vaccine-derived poliovirus reported across multiple provinces through February

Event

Health officials have reported elevated circulating vaccine-derived poliovirus (cVDPV) activity in Afghanistan, with 167 cases of cVDPV cases Nov. 11-Feb. 10. This is compared to no cVDPV cases reported over a similar period last year. Cases have been identified in multiple provinces: most recently, in Zabul, Uruzgan, Kandahar, Helmand, Gazni, Faryab, Farah, and Badghis. This report represents the most complete data available as of Feb. 16.

Context

Despite a significant improvement in the number of poliovirus cases over the past decade due to nationwide vaccination campaigns, this virus remains endemic to Pakistan and Afghanistan. The coronavirus disease (COVID-19) pandemic disrupted several vaccination programs, and vaccination coverage has therefore declined during 2020. As a result of this, a surge in the number of cases was observed toward the end of 2020, continuing into 2021.

The increase in the amount of cVDPV cases remains a concern. Cases of cVDPV are a rare result of widespread vaccination using oral polio vaccine (OPV), which contains a live but weakened strain of poliovirus. When a child is immunized with OPV, the weakened vaccine-virus replicates in the intestine for a limited time, leading to the development of antibodies. In areas of inadequate sanitation, vaccine-virus excreted by these children can spread in the community infecting susceptible individuals. To date, 303 cases of cVDPV have been reported in 2020, compared with zero cases for the whole of 2019.

Polio is highly infectious and can spread rapidly through contact with infected fecal material, such as in contaminated food and water. Infections are generally mild, but one in 200 cases leads to irreversible paralysis. Among those victims, 5-10 percent die when respiratory muscles become affected. The risk of paralysis increases with age. There is no specific treatment for polio.

Advice

Visit a doctor to receive a precautionary polio booster before traveling to Afghanistan, as even mildly symptomatic or asymptomatic people are infectious. Practice basic food and water precautions: drink only boiled, bottled, or purified water, and ensure that food is properly prepared and served hot.