Polio is a highly infectious virus that passes from person to person by the fecal-oral route. Because children’s’ dirty fingers often find their way into their mouths, this makes it easy for polio to spread. The virus can also survive in sewerage for many weeks. Communities with poor sanitation and hygiene are easy targets for the poliovirus. In most cases, the virus causes only a bout of fever and diarrhea. In perhaps one in a thousand cases, the child will develop severe paralysis in one or both legs, and it sometimes causes death. This is usually a lifelong disability and is especially damaging in many countries where there are very little supports or services for disabled people.
In 1988, the World Health Organization (WHO) and other agencies like USCDC, ROTARY, the Gates Foundation and UNICEF, decided to try to eradicate the virus entirely. Before 1988, there were around 200,000 cases of paralytic polio infection in children every year. The main tool in the eradication battle has been oral polio vaccine. OPV contains live poliovirus that has been weakened so it only very rarely (1 in a million doses) causes disease. The vaccine virus replicates inside the intestine and is excreted so that other family members are also vaccinated. There is also an Inactivated Polio vaccine (IPV) that is given as an injection.
IPV cannot cause paralysis because the virus has been killed. After a huge and costly global effort that has involved billions of OPV doses being administered to hundreds of millions of children, it looks like the world soon be polio free. Only Pakistan and Afghanistan still harbor wild poliovirus, and the number of cases is dropping fast. The polio eradication campaign has had many setbacks in the past so the world must remain vigilant. For the next few years even after the virus is eradicated, all young children will still need to keep being vaccinated until we are 100% sure the virus is gone forever! Have a look at this website for more information on this exciting public health effort.