A picture of the polio virus binding with human cells Credit: Science photo library
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On March 8 and 9, Sierra Leone recorded two cases of polio. This is the first case of polio in the country recorded since WHO declared Sierra Leone free from the virus in 2020. Sierra Leone’s last recorded case was in 2010.
Polio was the third disease to be eradicated from Sierra Leone. The other two are smallpox and Yaws. The latest strain of polio cases is known as Vaccine-derived poliovirus (cVDPV2)
Vaccine-derived polioviruses are rare. Experts say they circulate only due to low vaccination rates.
In May 2023, a WHO body, the Emergency Committee Under the International Health Regulation, listed Sierra Leone as one of the vulnerable countries to a case of circulating vaccine-derived polioviruses (cVDPV). The body recommended that the state declare the tracking chain of transmission a national health emergency among several measures.
The newly established National Public Health Agency (NPHA), which is leading the response effort, has said a risk assessment is needed and will determine whether this latest situation should be declared a public health emergency.
Sierra Leone has had its fair share of virus or disease outbreaks, from cholera and Lassa fever to ebola and polio. The latest outbreak has caused a fresh wave of concerns, especially for children not vaccinated to fight the virus. NPHA coordinates a response with the Ministry of Health, WHO, US-CDC, and UNICEF.
What is Polio?
The full name of the disease itself is poliomyelitis. Centre for Disease Control (CDC) defines Polio as a disabling and life-threatening disease caused by the poliovirus. It binds with cells in the human body and affects nerves in the spinal cord and other vital areas. The severe form of polio cases leads to paralysis, other physical debilitations and death.
According to WHO and other leading medical bodies, there is no cure; vaccination is the safest means of prevention against the disease.
The timeline of the new cases
On March 8, the NPHA announced that it had recorded a case of Polio Virus type 3 (PV3) in the northern district of Kambia. According to NPHA, the virus was found in a child who was “severely malnourished” and “shedding vaccine-derived poliovirus,” which is a rare occurrence, as stated in the press release. The virus was detected in the child’s stool.
The case was confirmed following testing the sample in CoteD’voire and South Africa to ensure it aligned with international standards. This current strain of polio is a circulating vaccine-derived poliovirus (cVDPV). The strain that was seen in Kambia is type 3 (cVDPV3).
On March 9, NPHA announced a second case. This new case was Polio Virus type 2 (cVDPV2) and was found in the capital, Freetown, in a slum community known as Marbella. The new case was discovered in sewage, following random testing in communities.
Credit: NPHA Facebook
Dr Thompson Igbu, Team Lead of the Expanded Program on Immunization for WHO in Sierra Leone, said in a separate press briefing on March 13 that one of the chains of transmission of the virus is through faeces.
“The virus can spread through faecal-oral transmission, contaminating water sources, food and water sources, particularly in areas with inadequate sanitation and hygiene practices.”
Response plan
Executive Director of NPHA, Prof Foday Sahr, said that the robust surveillance system they already have in place detected the case.
“Through our continuous and regular environmental surveillance, we were able to track down these cases and people they came in contact with,” he said during a government press briefing on March 12.
Sierra Leone’s vast experience with disease surveillance and brutal brushes with Ebola and COVID-19 has taught the country how to set up a robust national disease surveillance system, which is currently in use to tackle these polio cases. The Emergency Operations Center has raised the threat level to Level 2, which NPHA say will allow them to mobilise and track down the chain of transmission quickly.
Prof. Sahr said a comprehensive response plan is on the way, and vaccination will be a major part of that.
“We are working on a comprehensive response plan. We have deployed teams in both locations; surveillance and risk assessment are ongoing. We will continue to collect samples. We will also continue vaccinating and encouraging communities to participate fully in the polio vaccination,” Prof. Sahr said.
The response plan has seen a wide range of partners joining hands with the existing government establishments, from CDC to WHO and UNICEF.
NPHA has promised to scale up vaccination and outreach on hygiene habits in some of the most vulnerable communities.
Vaccination schedule
Two types of Polio vaccination regimens will be used: oral and injection. NPHA has issued public communication fliers explaining that four doses of Oral Polio Vaccine (OPV) and one dose of Inactivated Polio Vaccine (IPV) will be administered by injection.
NPHA says children should be brought to the hospital at birth, six weeks, ten weeks for the OPV and 14 weeks for the IPV.
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