The Ministry of Health for the United Republic of Tanzania alerted WHO on July 4 after detecting vaccine-derived poliovirus type 2 across the country. WHO has assessed the situation and determined that the national risk of the outbreak is high due to a lack of surveillance on vaccine coverage, resulting in low population immunity and ongoing population movement across neighboring countries.
Polio is a highly infectious disease that primarily affects children under the age of 5. It can cause permanent paralysis in approximately 1 in 200 infections and leads to death in 2-10% of those paralyzed.
The strain currently infecting individuals in Tanzania and some surrounding nations is a well-documented mutation of a strain found in man-made vaccines. In rare instances, the vaccine-derived virus can genetically change into a form that causes paralysis, similar to the wild poliovirus. This is known as a vaccine-derived poliovirus (VDPV), as stated by WHO in the emergency notice.
WHO highlights that the disease spreads through person-to-person contact, often through the consumption of food and water contaminated with fecal matter.
To combat the outbreak of the vaccine-derived virus, WHO recommends that anyone planning to visit or who has visited Tanzania or the Democratic Republic of Congo (DRC) should receive an additional vaccine.
According to WHO, the situation is concerning due to the lack of surveillance on vaccine coverage and the movement of populations across borders. The organization emphasizes the importance of maintaining high population immunity through comprehensive vaccination programs.