The World Health Organization reported today that a 19-month-old boy in Mali has polio. The child came to Mali from Guinea with his parents, and his polio infection is genetically linked to one reported in Guinea last year.
This particular strain of polio is vaccine-derived, which sometimes happens with oral vaccination. This type of vaccine uses weakened polio virus, which may sometimes mutate and make its way back into a community. Areas that are under-vaccinated are especially vulnerable. Still, circulating vaccine-derived polio is rare. According to the Global Polio Eradication Initiative, there were 580 cases out of 10 billion oral vaccine doses between 2000 and 2011.
Polio vaccinations dropped in Guinea in 2014 during the Ebola outbreak, which may have contributed to the current cases coming out of the region. Both Mali and Guinea are initiating an emergency response to the current outbreak. According to Lucien Manga, the acting WHO representative in Mali, the government there has set up emergency vaccination teams that will start immunizations on Wednesday. The government is also investigating the current case and conducting a risk assessment to see how it may potentially spread. “We are confident that the Government of Mali is taking appropriate measures to control this outbreak,” says Manga, via email.
The new outbreak follows celebratory announcements in July, when Nigeria hit a one-year milestone of remaining polio-free. At that time, it was thought that the virus would soon be eradicated from the entire continent, and that the only remaining strongholds were in Afghanistan and Pakistan. Now, in addition to the new Mali case, two new cases of vaccine-derived were reported in the Ukraine last week.
The new cases highlight the difficulties in reaching global eradication for any disease.
“These events mean basically that polio is not over until it’s over,” says Manga. “Stringent surveillance must continue, including in areas with satisfactory immunization coverage. We must ensure that all newborns are fully immunized—meaning that they receive 4 doses of the vaccine before the age of 7 months—and that the routine immunization activities must be strengthened.”