The detection in England of poliovirus, cause of the disabling and life-threatening polio disease, is raising eyebrows and provoking questions about how, where, and why now after 40 years?
Poliovirus and its variants are a global issue, but are found mainly in Afghanistan, Chad, Djibouti, Democratic Republic of the Congo, Malawi, Mozambique, Nigeria, Pakistan, Somalia and Yemen. The total number of infected countries with poliovirus is 29.
Seeing polio indicators in the UK is a bit of a surprise for some. The version of poliovirus that has surfaced in London sewage since February has been declared a national incident by the UK Health Security Agency. London as an outbreak “center” of the virus that causes polio is of intense interest because of the urban layout and connectivity to international airports and seaports.
No polio cases have been reported so far, nor any identified cases of paralysis. But sewage sampling in one London treatment plant has repeatedly detected closely related vaccine-derived polioviruses. The health agency says it is likely that closely linked individuals in north and east London are now shedding the type 2 poliovirus strain in their faeces.
Monitoring for diseases through this approach is important to understand. The UK agency monitors wastewater to check on the population’s health by analyzing environmental factors that affect the human system. Tests on British sewage typically pick up a handful of unrelated polioviruses each year. These come from people who have been given the oral polio vaccine in another country and then traveled to the UK. People given the oral vaccine can shed the weakened live virus used in the vaccine for several weeks.
The agency said the detections since February raised the alarm because the cases were related to one another and contained mutations that suggested the virus was evolving as it spread from person to person. The outbreak is believed to have been triggered by someone returning to the UK after having the oral polio vaccine, and spreading it locally. It is unclear how much the virus has spread; it may be confined to a single household or an extended family.
Surveillance of sewage water and monitoring in specific population neighborhoods is salient. The poliovirus can spread through poor hand hygiene and contaminated food and water, or less often through coughs and sneezes. A common route of transmission is for people to get contaminated hands after using the toilet and then pass the virus on by touching food consumed by others.
The strategy is to better plot the spread and alert health professionals to watch for any symptoms. Symptoms are flu-lile, to add to some other diseases circulating including COVID strains and perhaps even monkeypox. Increasing medical surveillance is picking up more findings because of increasing capabilities.
When discussing poliovirus, it is important to consider appearances of Acute Flaccid Myelitis; this type of poliovirus is more prevalent, but does not generate the headlines that polio does. AFM is a global polio-like neurological disease that lurks in the background of the disease threat matrix. Interestingly, the US still has no vaccine against the primary causative agent, enterovirus, while China has three, with more in Asia on the way.
As case reports rise, AFM is a growing concern in the US and other countries. The US has not had a case since 1979, but the heightened awareness is focusing on the fact that the West has yet to develop any vaccines and specifically targeted antiviral medications. In Asia, there are four vaccines in late-stage clinical trials. These vaccines protect against EV-A71, an enterovirus similar to EV-D68, two of the AFM series of acute flaccid paralysis. Three of these vaccines are licensed for use in children in China. A fourth vaccine is targeting a subject group in Vietnam.
Incidents in the West are negligible now, but the discussion about disease maintenance methods and reporting is facing a test over the coming years. COVID-19 changed the way in which health intelligence plays a role in measuring disease spread and its public perceptions.
Overall, the science of monitoring is improving, but pundit commentary can lead to too much speculation and fearmongering. So good judgment is needed to make informed decisions by all as another disease makes its media appearance.