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LONDON – The World Health Organization says a new polio outbreak in Sudan is linked to an ongoing vaccine-induced epidemic in Chad, a week after the UN health agency declared the African continent free of the wild virus of polio.
In a statement this week, the WHO said two children in Sudan, one from South Darfur state and the other from Gedarif state, near the border with Ethiopia and Eritrea, were paralyzed in March and April. Both had recently been vaccinated against polio. The WHO said initial investigations into the outbreak show the cases are related to an ongoing outbreak stemming from a vaccine in Chad that was first detected last year and is now spreading in Chad and Cameroon.
“There is local circulation in Sudan and a continuous exchange of transmission with Chad,” the UN agency said, adding that genetic sequencing confirmed numerous introductions of the virus into Sudan from Chad.
The WHO said it had found 11 additional cases of vaccine-derived polio in Sudan and that the virus had also been identified in environmental samples. Typically, there are many more unreported cases for every confirmed polio patient. The highly infectious disease can spread rapidly in contaminated water and most often affects children under 5 years of age.
In rare cases, the live polio virus in the oral vaccine can mutate into a form capable of causing new outbreaks.
Last week, the WHO and its partners declared the African continent free of the wild polio virus, calling it “an incredible and emotional day.”
On Monday, the WHO warned that the risk of further spread of vaccine-related polio in central Africa and the Horn of Africa was “high”, noting large-scale population movements in the region.
More than a dozen African countries are currently battling polio outbreaks caused by the virus, including Angola, Congo, Nigeria and Zambia.
Amid the coronavirus pandemic, many of the large-scale vaccination campaigns needed to eradicate polio have been halted in Africa and elsewhere, leaving millions of children vulnerable to infection.
In April, the WHO and its partners reluctantly recommended a temporary halt to massive polio immunization campaigns, recognizing that the move could lead to a resurgence of the disease. In May, they reported that 46 campaigns to vaccinate children against polio in 38 countries, mainly in Africa, had been suspended due to the coronavirus pandemic.
Some of the campaigns have recently been restarted, but health workers must vaccinate more than 90% of children in their efforts to eradicate the paralytic disease.
Health officials had initially aimed to eradicate polio by the year 2000, a deadline that was repeatedly delayed and missed. Wild polio remains endemic in Afghanistan and Pakistan; both countries are also struggling to contain outbreaks of vaccine-related polio.
