Health authorities in Malawi discovered an outbreak of wild poliovirus type 1 on Thursday. The announcement comes after a case was detected in a young child in Lilongwe.
Health authorities in Malawi discovered an outbreak of wild poliovirus type 1 on February 17. The announcement comes after a case was detected in a young child in Lilongwe, the country’s capital.
This outbreak is the first wild polio case the city has seen in over three decades, and it’s been over five years since a case has been identified in Africa. The Malawi government called the outbreak a public health emergency.
“The last case of wild poliovirus in Africa was identified in northern Nigeria in 2016, and globally there were only five cases in 2021,” said Dr Modjirom Ndoutabe, polio coordinator in the World Health Organization (WHO) Regional Office for Africa. “Any case of wild poliovirus is a significant event and we will mobilize all resources to support the country’s response.”
Teams of international disease investigators arrived in Malawi over the weekend to find out how the child caught the virus. They found the three-year-old girl in her home on the outskirts of the city, unable to move. She had reportedly been paralyzed since Nov. 19.
Investigators examined the virus’ genetic sequence and determined that it derived from a family of viruses that were seen circulating in Pakistan’s Sindh Province in October 2019. They do not currently know how the virus traveled from south Asia to Africa or how many others were infected during that time. The WHO is supporting the Malawi government to carry out an outbreak response, which will include supplemental immunization.
Polio invades the nervous system and can cause paralysis within hours of infection. As there is no cure for polio, vaccination is the only option for eradicating the disease, and live virus polio vaccine (OPV) is the method of choice for outbreaks.
In areas where immunity and vaccination rates are low, OPV can carry a substantial risk. Polio can spread as vaccinated children shed the weakened form of the virus, and if this goes unchecked, it regains the power to paralyze its victims. These are known as vaccine-derived viruses, and the type 2 virus in the vaccine is the most likely to regain virulence.
In 2021, 628 children were paralyzed as a result of the type 2 virus, mostly in Africa and the Middle East. Though this is a health emergency on its own, the potential spread of wild poliovirus in tandem with the vaccine-derived spread is concerning, to say the least.
Stool samples from the child in Malawi were collected one week after she was paralyzed, and she was initially diagnosed with type 2 poliovirus. The sample was sent to South Africa for additional testing, where the original diagnosis was found to be erroneous. The delay was said to be due to logistical obstacles in transportation worsened by the pandemic.
Increased efforts in testing and treatment of COVID-19 have also caused a backslide in surveillance of poliovirus. Though new polio outbreaks have been historically low in recent years, The WHO and The United Nations Children’s Fund (UNICEF) found that nearly 23 million children were unvaccinated or under-vaccinated against important childhood diseases in 2020.
“Even as countries clamor to get their hands on COVID-19 vaccines, we have gone backwards on other vaccinations, leaving children at risk from devastating but preventable diseases like measles, polio or meningitis,” said Dr. Tedros Adhanom Ghebreyesus, WHO Director-General.
The investigation team will continue their efforts to identify how the virus spread to Malawi and conduct emergency vaccinations efforts in the surrounding areas if necessary.
