Why polio is returning to Kenya

Kenya eliminated the indigenous wild poliovirus nearly 40 years ago in 1984.

But on Thursday, health officials reported two new polio cases of a different strain, bringing the total this year to eight. Two children are already paralysed.

Another suspected eight cases have been reported, and are being processed at the Kenya Medical Research Institute.

According to Dr Emmanuel Okunga, head of the division of disease surveillance and response, the Kemri polio laboratory has confirmed eight cases but is still carrying out analyses to confirm the other eight suspected cases. 

Is polio making a comeback? Yes and No. 

Dr Okunga said the wild polio, the virus that circulates naturally in the environment, was eliminated not just in Kenya but in Africa as well.

The current outbreak is linked to vaccine-derived strains of the virus.  

On extremely rare occasions, the weakened virus in the oral vaccine, when shed through stool, can infect an unvaccinated person and regain strength, becoming just as dangerous as the original virus. 

“All cases have been reported in Garissa County in Hagdera and Daadab Refugee camps,” Dr Okunga told the media on Thursday.

The cases sequenced so far have been traced to Somalia, where the infected refugee children came from.

The first cases were reported in May, rising to six in July.

In response, the Ministry vaccinated 1.9 million children in Kiambu, Kajiado, Garissa and Nairobi counties between August 24  and 28.

Mary Muthoni, the Principal Secretary for Public Health, said they are now planning two more rounds of vaccination.

“Sadly, there are clear indications that transmission of the virus is still active in Garissa County, especially within the refugee camps. Since our last meeting (August 2023), our surveillance system has detected an additional two polio cases, bringing the total number to eight,” she said.

Muthoni said they will conduct the second round on Saturday, October 7, to Wednesday next week.

“The upcoming round will target ten high-risk counties namely: Mandera, Wajir, Tana River, Lamu, Kitui, Machakos, Kiambu, Kajiado, Nairobi and Garissa, targeting 3,119,158 children under five years of age in all the targeted sub-counties,” she said.

Muthoni said in Fafi and Daadab sub-counties as well as all refugee camps in Garissa County, all children under 15 years will be vaccinated.

“For a long time, it has been assumed that polio largely affects children under five years of age. However, the confirmation of the virus in a seven-year-old child re-affirms that polio is a threat to all persons irrespective of age in areas where population immunity is compromised,” she said.

The final round of vaccinations will be done in November, but the date has not been set.

Although polio mainly affects children under five years of age, even unvaccinated adults can contract the disease.

There is no treatment and the disease is only prevented through vaccination.

“Every member of the public should report suspected polio cases among children under 15 years who develop sudden onset of weakness (paralysis) of the hands or legs or both without a history of injury to the nearest health facility or chief including nyumba kumi,” Muthoni said.

Last year, globally, there were nearly 800 cases of vaccine-derived polio, according to the Global Polio Eradication Initiative.

Of the 15 polio cases reported in the first quarter of 2023, 14 are from strains of the virus that mutated from the oral polio vaccine used in lower-income nations such as Kenya.

This vaccine is made with a living, weakened virus.

It is preferred because it is cheap and easy to administer. Two doses confer lifetime immunity.

The WHO says the vaccine itself does not cause the disease so there is completely no risk when one is immunised with it.

However,  children immunised with it can shed the live virus in their stool, which can then spread through sewage in places with poor sanitation.

If the virus stays weak, it can expose an unvaccinated person to polio and give them immunity. But if the virus mutates and regains virulence, someone who is not vaccinated can become sick with vaccine-derived polio after contact with the contaminated wastewater.

Initial symptoms are fever, fatigue, headache, vomiting, stiffness of the neck and pain in the limbs.

“One in 200 infections leads to irreversible paralysis (usually in the legs). Among those paralysed, five–10 per cent die when their breathing muscles become immobilised,” the WHO says.

Experts have also developed a safer, novel oral polio vaccine, which contains a virus that has been weakened so much that it may not even resuscitate under most circumstances.

There is also the inactivated poliovirus (injectable) vaccine used in developed countries which is extremely effective. It requires four injections. But is expensive and requires trained medical staff to carry out such campaigns.