If asked, would you rank polio among the world’s most severe infectious diseases?
No, I wouldn’t either - but it’s worth remembering that it took a lot of hard work to get it off of that list. Poliovirus, a human enterovirus of the family Picornaviridae, has persisted throughout history with fascinating success. It can be seen everywhere from ancient Egyptian paintings and carvings of otherwise healthy people with withered limbs, to, more recently, the 20th century polio epidemics that became a seasonal plague, paralysing children and adults alike and causing the ultimate race for a vaccine. While 90-95% of poliovirus infections are asymptomatic, the symptoms of polio - when they present - are both devastating and deadly.
Several poliovirus vaccines have been developed to date; in particular, one live, attenuated vaccine and one IPV (inactivated poliovirus vaccine). In a recent Nature News article, "A war not yet won", the financial implications of poliovirus - which is still endemic in developing countries, despite a worldwide push for eradication - were examined alongside various strategies for moving forward with changes to the proposed eradication scheme. One such change was the use of the injectable IPV vaccine in conjunction with the oral vaccine - the live, weakened attenuated virus - that’s currently being used to treat poliomyelitis in endemic populations.
Although the fight to eradicate poliovirus is far from over - and it’s definitely too early to start congratulating - complementing the inexpensive, highly effective oral vaccine with its injected dead-virus counterpart is a promising start. With sufficient funding and a better global understanding about the benefits of vaccination, we’ll see the end of poliomyelitis in our lifetimes.
Top Image: Coloured transmission electron micrograph (TEM) of clusters of polio viruses, the cause of poliomyelitis (infantile paralysis). There are three serotypes of the polio virus; pictured here is type 1, which causes most epidemics.
Bottom Image: A computer’s 3D rendering of poliovirus virions.