Polio detection puts a damper on years of hard work

Kenya’s effort to be declared a polio free country this year has been pushed back by three years following discovery of the infectious virus in parts of Nairobi city last month.

The Ministry of Health last week issued an alert after a team of experts from the Kenya Medical Research Institute (Kemri) and Centre for Disease Control (CDC) reported that they found traces of the virus in sewage samples collected in Eastleigh in March.

Through a statement to county directors of health, Director of Medical Services Jackson Kioko warned that the virus, known as circulating vaccine-derived polio virus type 2, has the capacity to cause paralysis in un-immunised people.

CARRIERS

“In view of this confirmation, the ministry wishes to put all health workers on alert for a potential outbreak by this type of virus,” said Dr Kioko.

Speaking to the Nation, Dr Kioko said the ministry’s concern was that there could be some individuals who are carriers of the virus in the country and, therefore, the need to have mass vaccination.

“We do not know if the individual came and left or is still in the country but, from our observations and genetic sequencing, the virus is similar to that causing an outbreak in Somalia,” he said.

The particular virus is commonly found in a weakened form in the oral polio vaccine. Currently, the oral polio vaccine made from a live polio virus is given to children in three doses: At two months, four months and the last at between the ages of six and 18 months.

The country further introduced an injectable version of the vaccine in 2015, and replaced the oral vaccine which gave protection against the three types of polio with one that only offers protection against two types of polio.

KEMRI

This is because the second type of polio was eradicated globally in 1999.

“We suspect that those children who have not received the Injectable Polio Vaccine could be excreting the weakened polio virus they got during immunisation. The only way to know if the virus is still circulating is by conducting environmental surveillance,” said Dr Kioko.

Whereas the weakened virus does not affect the person vaccinated as the individual develops immunity against it, when excreted into the sewage it has the potential of causing an outbreak in a population with weak immunity, said Dr Kioko.

According to experts, the discovery means there are children who, despite not being sick from polio, may be carrying the virus. “We are not as worried about finding the virus in the environmental samples as we are about knowing there could be a population of asymptomatic children who have the virus in them,” explained Dr Peter Borus, who heads the Kemri polio laboratory.

The findings, they added, is a stark reminder immunisation of children cannot stop, especially at a time when vaccine-derived polio virus is being detected in the environment.

RISK

Kenya was to defend its submission to the Africa Regional Certification Commission (ARCC) for polio eradication to be certified as polio free this year in June. But with the current discovery, it is now considered one of the countries at risk of an outbreak like Nigeria, DRC Congo, Ethiopia, Somalia and Chad.

“Until we address the situation, it will be difficult for us to defend our case,” said Dr Borus.

World Health Organisation country representative Dr Rudi Eggers described the researchers’ findings as a setback that will slow down the African region’s process of certification.

“This means the continent will have to wait for another three years, before submitting a certification request,” said Dr Eggers.

PARALYSIS

Polio is an infectious disease caused by the poliovirus and is transmitted through contaminated water or food, or contact with an infected person.

Many people who are infected with the poliovirus do not become sick and have no symptoms. However, those who do become ill develop paralysis, which can sometimes be fatal.

The last polio case in Kenya was reported in 2013, where 14 people were found to be infected with polio from Somalia. But this is not the first time that this virus is being found in the environment, as two years ago, Kemri reported traces of a vaccine-derived polio virus in environmental samples collected in Eastleigh, Kibera, and Mathare sub-counties.

In areas of inadequate sanitation, like the three areas among others, the excreted vaccine-virus can spread in the immediate community (to offer protection to other children through ‘passive’ immunisation), before eventually dying out.

IMMUNITY

Whereas no cases have been detected yet, experts are worried that without good population immunity, the virus detected in Eastleigh has the potential of causing an outbreak. This is because the samples collected showed that the virus has “mutated and reversed to virulence.”

If not properly addressed, the experts went on to say, there is reason to worry about resurgence of the disease.

But why is it that this virus is often detected in areas like Mathare, Kibera and Eastleigh?

A vaccine-derived polio virus is a rare type of poliovirus that has genetically mutated from the live weakened strain contained in the oral polio vaccine.

A day or two after children are given the polio drops, the weakened virus in the vaccine is shed in stool and should die off after 14 days, explained Dr Borus.

MIGRANTS

But in places like Eastleigh where there is low immunity, the vaccine can survive longer and in the process mutate to its harmful nature, posing a risk to the entire community.

These areas create a thriving environment for this virus, as the places are densely populated, have an influx of migrant populations, yet, they also have poor sanitation.

Environmental viruses

“Often when we trace back the virus, we find that Daadab, Eastleigh and Garissa will test positive for environmental viruses because of the migrant population from Somalia,” he said.

Coupled with low or poor immunity, the virus will survive longer in the environment compared to areas where there is a high vaccination coverage.

Kenya is among sub-Saharan African countries that have made significant progress towards polio eradication though the threat of an outbreak remains huge due to influx of refugees from strife-torn neighbouring countries where the disease is endemic.

INJECTABLE

“The refugees will not access medical services as they fear being identified by authorities as undocumented migrants, posing a risk to the whole community and country,” explained Dr Borus.

He also notes the use of the oral polio vaccine that has a live but weakened (attenuated) virus also comes with it fair share of challenges. Kenya introduced an extra dose of injectable inactivated polio vaccine (IPV) in 2015, a vaccine commonly used in most developed countries, like the US and Canada. The introduction was in readiness to transition from the live polio virus.“At the end of the day, the attenuated vaccine will be phased out to give way for the IPV but for now, to offer children full immunity, we need both the oral and injectable vaccine,” explained Dr Borus.

Since the last meeting by an advisory team from the Horn of Africa Technical Advisory Group for Polio Eradication in May last year, the incidence of polio has changed in the region.

For instance, like Kenya, Somalia detected two types of vaccine-derived polio viruses in its environmental site raising the risk for the spread of the polio disease in the region.

Based on the latest reported case, the World Health Organisation (WHO) now wants the country to review and make recommendation on its surveillance to high risk and mobile population, provide risk mitigation strategies.

As a result, a vaccination campaign has been planned for Nairobi County from May 5 to 9 targeting about 815,000 children under the age of five.