Polio: What You Need to Know About the Nearly Eradicated Disease

Polio, also known as poliomyelitis, is a contagious disease that can cause paralysis and death. Polio is caused by the poliovirus, which can infect the nervous system and damage the spinal cord and brain. Polio mainly affects children under the age of five, but anyone can get infected if they are not vaccinated.

In this article, we will explain what polio is, how it is transmitted, how it is diagnosed and treated, and how to prevent and control it.

What is polio and what causes it?

Polio is an infectious disease caused by the poliovirus, a member of the enterovirus family, which also includes the viruses that cause hand, foot, and mouth disease and the common cold. The poliovirus has three types: type 1, type 2, and type 3, which differ in their genetic makeup and virulence. Type 1 is the most common and the most dangerous, as it is responsible for most cases of paralysis and death.

The poliovirus was first discovered in 1908 by the Austrian immunologist Karl Landsteiner and the German physician Erwin Popper, who isolated the virus from the spinal cord of a child who died of polio. Since then, the poliovirus has caused several epidemics around the world, especially in the 20th century, when it became one of the most feared childhood diseases.

How is polio transmitted?

Polio can be transmitted in several ways:

• Through the fecal-oral route. This can happen when people ingest food or water that is contaminated with the feces of an infected person. This is the main mode of transmission of polio, as the poliovirus can survive in the environment for a long time and can spread easily in areas with poor sanitation and hygiene.
• Through the oral-oral route. This can happen when people come into contact with the saliva or respiratory secretions of an infected person. This is a less common mode of transmission of polio, but it can occur in crowded settings or during close contact, such as kissing or sharing utensils.
• Through contact with infected animals or their products. This can happen when people handle, slaughter, or consume animals that carry the poliovirus, such as monkeys or pigs. This is a rare mode of transmission of polio, but it has been reported in some countries, such as China and Nigeria.

The risk of transmission of polio depends on several factors, such as the type and strain of the poliovirus, the immune status and vaccination history of the exposed person, and the environmental conditions and season. The incubation period of polio, which is the time between exposure and onset of symptoms, ranges from 3 to 35 days, with an average of 12 days. People are infectious from 7 to 10 days before and after they develop symptoms, but they can also transmit the virus without showing any symptoms (asymptomatic carriers).

How is polio diagnosed and treated?

Polio can be diagnosed by clinical examination and laboratory testing. The clinical signs of polio include:

• Fever, headache, sore throat, and fatigue
• Muscle pain, stiffness, and weakness, especially in the legs
• Paralysis, which can affect one or more limbs, the face, the diaphragm, or the whole body

The paralysis of polio is usually asymmetric, meaning that it affects one side of the body more than the other. The paralysis can also be flaccid, meaning that the affected muscles are limp and floppy, or spastic, meaning that the affected muscles are tight and contracted. The paralysis can be temporary or permanent, and it can occur suddenly or gradually.

To confirm the diagnosis of polio, laboratory testing is needed. The preferred method is to detect the poliovirus in a sample taken from the throat, the stool, or the cerebrospinal fluid, using a technique called polymerase chain reaction (PCR). This test is highly accurate and sensitive, but it may take several days to get the results. Other methods, such as culture or serology, may not be reliable, as they do not distinguish between different types of poliovirus or between wild and vaccine-derived poliovirus.

There is no specific treatment for polio, and most people recover without complications. The aim of treatment is to manage the symptoms and prevent secondary infections or complications, such as respiratory failure, urinary tract infection, or post-polio syndrome. The treatment options include:

• Antipyretics and analgesics, such as paracetamol or ibuprofen, to reduce fever and pain
• Muscle relaxants, such as diazepam or baclofen, to reduce spasm and stiffness
• Physical therapy, such as massage, stretching, or exercise, to improve muscle function and prevent contractures
• Orthopedic devices, such as braces, splints, or crutches, to support the affected limbs and improve mobility
• Ventilatory support, such as oxygen therapy or mechanical ventilation, to assist breathing in case of respiratory paralysis

The treatment for polio may vary depending on the severity of the disease, the availability of the resources, and the local guidelines. Some of the treatments are only supportive and palliative, and they do not cure the disease or reverse the paralysis.

How to prevent and control polio?

The best way to prevent and control polio is to get vaccinated. Vaccination is the most effective way to protect yourself and others from polio. Vaccines can induce immunity and prevent infection, transmission, and paralysis. However, no vaccine is 100% effective or safe, and some people may not respond well to the vaccine or may lose their immunity over time. Therefore, vaccinated people should still follow the other preventive measures and monitor their symptoms.

There are two types of polio vaccine: the inactivated polio vaccine (IPV) and the oral polio vaccine (OPV). Both vaccines contain weakened or killed poliovirus, but they have different advantages and disadvantages.

• The IPV is an injectable vaccine that contains killed poliovirus. The IPV is safe and effective, and it does not cause vaccine-associated paralytic polio (VAPP) or circulating vaccine-derived poliovirus (cVDPV). However, the IPV is more expensive and requires trained health workers and sterile equipment to administer. The IPV also does not provide mucosal immunity, meaning that it does not prevent the virus from multiplying in the intestine and being shed in the feces.
• The OPV is an oral vaccine that contains live attenuated poliovirus. The OPV is cheap and easy to administer, and it provides mucosal immunity, meaning that it prevents the virus from multiplying in the intestine and being shed in the feces. However, the OPV can cause VAPP or cVDPV in rare cases, especially in areas with low vaccination coverage or poor sanitation. The OPV can also interfere with the immune response to other vaccines or infections.

The WHO recommends that all children receive a combination of IPV and OPV to achieve optimal protection against polio. The recommended schedule is to give one dose of IPV at 14 weeks of age, followed by three doses of OPV at 6, 10, and 14 weeks of age, and a booster dose of OPV at 9 months of age. Additional doses of OPV may be given during supplementary immunization activities (SIAs) or outbreak response campaigns.

Other preventive measures to reduce the risk of polio include:

• Practicing good hygiene and sanitation, such as washing hands with soap and water, using safe water and food, and disposing of feces properly
• Avoiding contact with people who have polio or who are not vaccinated, especially if they have symptoms or live in endemic or outbreak areas
• Reporting any suspected cases of polio to the local health authorities and cooperating with the surveillance and investigation activities
• Supporting the global polio eradication efforts, such as the Global Polio Eradication Initiative (GPEI), which aims to stop the transmission of wild and vaccine-derived poliovirus and certify the world as polio-free by 2023

Conclusion

Polio is a serious and preventable disease that can cause paralysis and death. It is caused by the poliovirus, which can infect the nervous system and damage the spinal cord and brain. It is transmitted mainly by the fecal-oral route, but also by the oral-oral route or by contact with infected animals. It can cause mild to severe symptoms, and sometimes no symptoms at all. It can be diagnosed by clinical examination and laboratory testing, and treated by symptomatic and supportive care. It can be prevented and controlled by getting vaccinated and following the public health measures, such as hygiene, sanitation, isolation, and reporting.