The Fight against Polio
The poliovirus is one of the smallest and simplest viruses. It is usually spread by just dirty fingers and in most cases is confined to the gut. As the virus travels down the intestine, it induces the body to produce antibodies against it, which will protect the person against future attacks. In about one per cent of cases, the virus floods into the bloodstream and infects the nerve cells in the spinal cord that drive the muscles. This causes the characteristic paralysis, which can affect one or more limbs and/or the muscles of respiration, in which case artificial ventilation, for example with the iron lung, may be needed to keep the patient breathing and alive. The iron lung, which was officially known as a negative pressure ventilator, was invented hundreds of years ago, but was further developed in the 1930’s to help with the world polio outbreaks. At one point, the need for iron lungs was so high that they were used with a patient within an hour of their manufacture.
Polio originally caused sporadic clusters of paralysis, especially in children. For some reason, this pattern changed during the late nineteenth century into explosive epidemics, which swept through many countries each summer. The first major outbreak, on the East Coast of the USA in the summer of 1916, caused 25,000 cases of paralysis and 6,000 deaths. Draconian public health measures were powerless to prevent the spread of the disease, resulting in widespread panic across America. Each year, panic resurfaced as the polio season approached, with the wealthy leaving towns and cities in droves.
This fear of polio was deliberately fuelled and exploited by the March of Dimes, an American fund-raising organisation set up by President Franklin D Roosevelt, himself a polio survivor.
The March of Dimes raised vast sums, and funded both practical support for polio victims and their families, and the research programmes that ultimately resulted in effective polio vaccines.
Polio can be prevented but not cured. Treatments proposed for patients with acute polio have included barbaric measures, such as branding the child’s back with a red-hot poker and ‘brain washout therapy’. Less dramatic were massive doses of vitamins C and chemically modified cobra venom. None of these had any impact on paralysis or survival, and some were positively dangerous. The iron lung could rescue patients from suffocation if their respiratory muscles were paralysed, but the iron lung itself carried considerable risks. Until chest infections could be properly treated, seventy per cent of patients put inside the iron lung died there.
Two rival strategies were used to develop vaccines to protect against polio. Jonas Salk
(1914–1998) favoured an ‘inactivated polio vaccine’ (IPV), in which wild polioviruses are ‘killed’ with formalin, so that they can no longer replicate and spread into the spinal cord. IPV is injected into a muscle and causes protective antibodies to appear in the bloodstream.
The ‘oral polio vaccine’ (OPV) developed by Albert Sabin (1906–1993) relies on the fact that polioviruses forced to grow under unfavourable conditions in the laboratory will undergo mutation into forms that can no longer invade the spinal cord. The OPV virus is still ‘alive’ and able to replicate, but cannot enter the spinal cord and cause paralysis. OPV is taken by mouth and, like a wild poliovirus, induces immunity against itself in the gut wall as it travels through the intestine. It therefore provides a different type of immunity protection when compared with the Salk vaccine.
Salk’s IPV was the first polio vaccine to be tested on a large scale, in massive clinical trials in 1954 involving 1.8 million American children. Following the sensational declaration that his vaccine ‘works and is safe’, Salk became a national and international hero, and mass vaccination of children with his IPV began immediately. Vaccination continued despite a tragic outbreak of paralytic (and sometimes fatal) polio due to contamination of the Salk vaccine with wild poliovirus, which was the result of carelessness in the vaccine production plant.
Numbers of paralytic cases and deaths from polio fell dramatically in the USA over the next few years, and Salk’s vaccine was taken up across the world. Sabin’s OPV, being cheaper, more effective and easier to give, later superseded the Salk vaccine. Given correctly, both vaccines protect against polio and are overwhelmingly safe. There is an exceedingly low risk (one in 500,000 vaccinations) of Sabin’s OPV reverting to a paralysing variant, a drawback that Sabin always refused to acknowledge.
Polio vaccine not only protects individuals, but, if given intensively and on a massive scale, can prevent the virus from spreading and so stamp it out. In 1988, various organisations set out to clear the planet of polio through a worldwide vaccination campaign. The hope was that polio would follow the example of smallpox, which was exterminated by intensive global vaccination during the late 1970’s. Now, after 26 years, polio is tantalisingly close to being eradicated, with just 200 paralytic cases worldwide last year, as compared with over 300,000 in 1988. Tragically, though, endemic polio continues to cling on in three areas, Afghanistan, Pakistan and Northern Nigeria, largely because of anti-western ideology that is backed up by intimidation, death threats and the murder of many vaccinators and their supporters. Usually refugees, but also other travellers, have reintroduced polio to other countries, for example Syria, Lebanon and various African states, which had been previously cleared of polio.
Unfortunately, it is now very unlikely that polio will be eradicated within the next two to three years and it seems that the final extermination of the virus will depend as much on diplomacy as on medicine and science.
Questions 1 – 7
The text above has 7 paragraphs A - G.
Which paragraph contains the following information?
Write your answers in boxes 1 – 7 on your answer sheet.
1.The OPV protects people in the same way as a wild virus works in the body.
2.Panic was intentionally created in order to raise money to fight polio.
3.The OPV was more successful than the IPV at preventing polio.
4.The US polio outbreaks caused some people to move away from high population areas in the summers.
5.Extremism is one barrier to the eradication of polio.
6.Iron lungs were in great demand because the numbers of people sick with polio.