Nigeria: Polio activity reported in additional states during November. /update 3

Event

Health authorities identified 122 additional cases of circulating vaccine-derived poliovirus type 2 (cVDPV2) in Nigeria Sept. 24-Nov. 10, including the first cases identified in Edo State and the Federal Capital Territory, bringing the total to 274 cases since Jan. 1. This is compared to three cases reported over a similar period during 2020. Officials have observed cases of cVDPV2 during 2021 in at least 22 states, with Jigawa, Kebbi, Kano, and Borno reporting the most cases. The risk of transmission is present nationwide. This represents the most complete data available as of Nov. 12.

Context

Officials reported sporadic cases of circulating vaccine-derived poliovirus (cVDPV) in Nigeria, with eight cases in 2020, 18 in 2019, and 34 in 2018. Nigeria was declared free of wild poliovirus in 2020; however, fluctuating levels of vaccine coverage against polio may cause flare-ups of cVDPV in susceptible communities. 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 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.

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 Nigeria, 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.