Mali is on high alert after a baby was found to have the highly contagious, crippling polio virus, the World Health Organization said Monday, blaming low vaccination coverage.
"A case of circulating vaccine-derived poliovirus type 2 (cVDPV2) has been confirmed in Bamako," WHO said in a statement.
Mali authorities had detected polio in a 19-month-old child from Guinea, who was brought to Bamako for medical treatment seven days after paralysis set in on July 20, the UN health agency said.
There was a case of wild poliovirus in Mali in June 2011 in the Timbuktu region.
Monday's announcement came less than a month after Africa marked one year since the last recorded case of wild polio, which raised hopes the continent was moving towards eradicating the crippling disease that usually impacts young children.
But while there have been no cases of wild polio in Africa since August 11, 2014, there have been several cases since then, in Madagascar and Nigeria, of vaccine-derived variants like the one found in Mali, WHO spokesman Oliver Rosenbauer told AFP.
Two polio cases confirmed in Ukraine last week were also due to a type of vaccine-derived poliovirus.
Vaccine-derived polio infections are in rare cases caused by one type of polio vaccine, which contains small amounts of weakened but live polio virus.
Oral polio vaccine (OPV) replicates in the gut and can be passed to others through faecal-contaminated water, thus imperilling unvaccinated children.
WHO has recommended that OPV be phased out worldwide and replaced by the inactivated polio vaccine (IPV).
The latest case is genetically linked to a confirmed case of the virus detected in the Siguiri district, in the Kankan Region of Guinea, in August 2014, which appears to have been circulating undetected across international borders for more than two years, WHO said.
"The risk of spread of this virus is deemed high and it has the capacity to cause paralytic disease in humans or kill," the agency said, warning that the emergence of the virus revealed "low population immunity against the virus due to low rates of vaccination coverage in Guinea."
WHO said that the oral polio vaccine must now be administered "multiple times to stop the outbreak and protect children."
WHO said that it was helping the health ministries in both Mali and Guinea to investigate the circumstances behind the emergence and spread of the virus, and to mount a robust vaccination campaign to put an end to the outbreak.
"It is highly important for communities to ensure that all under-five children are vaccinated during the three rounds of polio campaigns," the agency said, adding that the first vaccination round would begin this week in Mali and within two weeks in Guinea.