At its worst, polio causes paralysis: ‘Polio Paul’ Alexander had to live in an iron lung for 70 years after surviving the disease as a child. In Pakistan and Afghanistan, where polio is endemic, children are still at risk. Polio is a highly contagious viral disease caused by poliovirus. It can cause permanent disability and even death, especially in children under five years of age. Two types of polio exist in the world today: wild poliovirus and vaccine-derived poliovirus. The latter is derived from an oral polio vaccine, known as the Sabin vaccine or OPV.
Wild poliovirus has been eradicated in most countries except Afghanistan and Pakistan. Vaccine-derived poliovirus has been found in Yemen and Central Africa. There are three types of viruses, both wild and vaccine-derived forms – types 1, 2 and 3. Although vaccine-derived polio can take the form of any of three types, type 1 is the only remaining form of wild poliovirus. (Also read: Polio Day on March 3, 2024: 5 benefits of polio vaccine for your child ,
Types 2 and 3 were declared eradicated in 2015 and 2019. Although all wild poliovirus types can cause similar symptoms, there are differences in how harmful they can be, and immunity to one type does not protect against other types.
what are the symptoms?
Most people infected with polio are asymptomatic. About one in four people experience flu-like symptoms, such as sore throat, fever, headache or stomach pain. Generally, these symptoms go away on their own after two to five days.
Although it is rare, a very small percentage of people infected with the polio virus – less than 1% – experience very dangerous symptoms, such as permanent paralysis, which can lead to permanent disability, and even death. Can occur when the virus affects the muscles needed for breathing.
Sometimes children who fully recover may later develop post-polio syndrome as adults, characterized by new muscle pain, weakness, or even paralysis.
How is polio spread?
This virus infects the intestines and throat of the person. It can survive there for several weeks. It spreads in a community through contact with respiratory droplets or feces of an infected person. In places with poor sanitation, the virus can also contaminate food and drinking water. Infected people can spread the virus to others just before and up to two weeks after symptoms appear.
Where does polio exist today?
Polio has still not been eradicated worldwide – wild forms of the virus still exist in Afghanistan and Pakistan. And although Africa has been considered free of wild polio since August 2020, imported cases have been reported in Malawi and Mozambique.
In July 2022, the US reported its first case of vaccine-derived polio in a decade. Vaccine-derived poliovirus was also found in sewage samples in the UK and Israel. “It was a stark reminder that if we do not meet our goal of eliminating polio everywhere, it could re-emerge globally,” WHO Director-General Tedros Adhanom Ghebreyesus said at the time.
Thanks to the development of polio vaccines and aggressive global vaccination campaigns in the mid-20th century, more than a hundred countries have been declared polio-free.
What are the two types of polio vaccine?
There is no cure for polio, but there are vaccines to prevent the disease: oral polio vaccine (OPV) and inactivated polio vaccine (IPV). Oral polio vaccine is given as an oral liquid and is important for international eradication because it protects the person and stops the virus from spreading. OPV uses live but weakened forms of poliovirus that are modified to not cause disease in the person receiving the vaccine.
But if the OPV-weakened virus is able to survive and spread in places with poor sanitation, such as in waste water, where there are large numbers of unvaccinated people, it could revert to a disease-causing form of the virus.
Inactivated polio vaccine is given as an injection and is highly effective in protecting the recipient from severe disease. Because it is inactivated, it cannot cause vaccine-derived polioviruses. However, unlike OPV, it does not stop the spread of the virus if the person is already infected.
OPV is cheaper than IPV and does not need to be administered by a health professional. But more and more countries are using IPV because of the threat of vaccine-derived poliovirus. There are some types of care that can help with the symptoms caused by polio, such as bed rest, pain-relieving medications, breathing assistance, and physical therapy.
