Sierra Leone: Additional cases of circulating vaccine-derived poliovirus reported in the north and western areas of the country. /update 1

Event

Health authorities in Sierra Leone reported five additional cases of circulating vaccine-derived poliovirus type 2 (cVDPV2) in the country on March 10, bringing the total to 8 cases since the disease was first reported on Dec. 12, 2020. Cases have occurred in the Northern and North Western provinces, and in the Western Area. This represents the most complete data available as of March 17.

Context

These are the first known cases of cVDPV2 in Sierra Leone. The country reported one case of wild poliovirus (WPV) in 2010 and 11 WPV cases in 2009. Cases of cVDPV are a rare result of widespread vaccination using oral polio vaccine (OPV), which contains a live but weakened poliovirus strain. When a child is immunized with OPV, the weakened vaccine-virus replicates in the intestine for a limited time, leading to antibodies' development. In areas of inadequate sanitation, vaccine-virus excreted by these children can spread in the community.

Polio is highly infectious and can spread rapidly through contact with infected fecal material, such as contaminated food and water. Infections are generally mild, but 1 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.

The risk of healthy individuals contracting polio from contaminated food or water remains negligible. Still, individuals with compromised immune systems or those suffering from long-term illness may be more susceptible.

Advice

Visit a doctor to receive a precautionary polio booster before traveling to Sierra Leone, 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.