While the 11th day of the 11th month is now best known as Remembrance day, a few other significant events have taken place on this day in the course of recent history. Most notably, the 11thof November marks the date the Polio virus was first identified and photographed in Cambridge, Massachusetts.
The polio virus causes poliomyelitis, which has devastating consequences on small children and adults alike, leading to paralysis, loss of function of limbs and, in a significant proportion of cases, death. While in 2015 the recorded cases of poliomyelitis worldwide were only 66, prior to the introduction of an emergency vaccination programme in the 1950 poliomyelitis was one of the most severe threats to human health on the planet. In the late 1970, over half a million people in the Western World were paralysed as a consequence of polio infections: during the great epidemic of 1952, over 3 thousand people died and 21 thousand people were paralysed by the debilitating effect of the disease. It therefore comes as no surprise that American medical science was concentrating on poliomyelitis and its causes in the second half of 1953.
Like most enteroviruses, the polio virus is composed of a capsule made of simple protein replicates, which contains a small stretch of RNA. The RNA in questions encodes all the information the virus needs to replicate, using the sophisticated machinery of a “host” human cell to translate this information into protein. The virus works by tricking the host cells into engulfing the viral capsule, subsequently releasing the positive-strand RNA contained within. This RNA strand can access the same machinery that transforms mRNA into protein during the normal functioning of a cell – a cell organ known as the “ribosome” can read the strand of RNA and produce protein that matches the information encoded within the RNA strand. In particular, these proteins include machinery to replicate the viral-RNA strand (and therefore reproduce, making thousands of viral particles for a single infecting virus) and proteins that form the capsule encasing the viral RNA. After this process is complete, the virus essentially “explodes” the host cell, killing it in the process and releasing tens of thousands of newly produces viral particles in the body, leading to further infection.
While the most common course of the disease sees the virus infecting cells of the gastro-intestinal tract and leads to moderate to undetectable symptoms, in a minority of patients the infection can extend to the central nervous system (CNS), namely the spine and the brain. Viral particles in the CNS infect nerve cells and, once they are ready to move on, “explode” them resulting in a nerve damage and eventually paralysis or, in the most serious cases, death. Famous victims of poliomyelitis-derived paralysis include President Franklin D. Roosevelt, who was famously bound to a wheelchair as a consequence of the infection.
The year before the virus was first imaged, Dr Salk at the University of Pennsylvania developed a potential vaccine against the polio virus. Two years after, in 1955, the polio vaccine was found to be safe and efficacious as a result of extensive clinical trials – this started a campaign that slowly but surely erased polio first from the United States and subsequently from most of the world. India was the last major hurdle, and it took until 2014 for the WHO to declare it polio-free.
We live in difficult times for the pro-vaccine movement. Unscientific, inflammatory rhetoric is spreading through the Internet to benefit the peddlers of “alternative remedies” and harming children (and parents) everywhere. The recent resurgence of mumps and whooping cough epidemics has shown that all we have achieved in looking after human health has never been so valuable and in need of more militant protection.
Written by: Gaia Cantelli