Polio – also known as infantile paralysis – is a highly contagious viral disease. Often, there are no specific symptoms. In severe cases, paralysis of the legs or even the respiratory muscles may occur as a result of the disease. Polio has been considered eradicated in Europe since 2002, yet two cases occurred in Ukraine in September 2015. This highlights the importance of vaccination to prevent a resurgence of the viral disease. Until 1998, two different vaccines against polio were available. Today, only the IPV vaccine developed by Jonas Salk, which is injected intramuscularly, is used. The oral vaccine, on the other hand, is no longer used in Germany because in rare cases it itself caused polio.
What is polio?
Polio is a disease caused by the highly contagious poliovirus. Those infected with the virus can be contagious themselves within hours of infection and remain so for up to six weeks. How long it takes for the disease to break out can vary widely: Usually, the incubation period is between three and 35 days. The virus is predominantly transmitted fecal-orally. In this respect, polioviruses are similar to the pathogens that cause hepatitis A. Fecal-oral means that the pathogen is excreted in the stool of infected persons. Due to poor hygiene, the viruses can then get onto objects or liquids and be reabsorbed via the mouth (orally) in this way. Droplet infection through sneezing or coughing is possible but relatively rare.
Polio: symptoms nonspecific
Polio often progresses either without any symptoms at all or at least without any clear symptoms. Those affected then usually do not even notice that they are infected with the virus. They experience only nonspecific symptoms of illness, such as fever, sore throat, loss of appetite, nausea, and diarrhea. This phase can last between one and two weeks – in many cases the illness subsides afterwards. If the viruses penetrate the central nervous system, symptoms such as fever, back pain, neck stiffness and muscle aches may occur about three to seven days after the end of the first phase. Some affected individuals – estimated to be between 0.1 and 1 percent – subsequently experience the paralysis symptoms typical of polio. These are asymmetric paralyses that usually remain even after the disease has subsided. The paralyses primarily affect the legs. However, the virus can also affect other muscles, for example in the arms, eyes or abdomen. If the paralysis spreads to the respiratory muscles, the patient may die. A severe course is more likely in adult patients than in children.
Post-polio syndrome
After surviving polio, the so-called post-polio syndrome may occur later in life, sometimes years or decades later. This syndrome may become apparent even if the polio illness itself has passed without symptoms. In the course of post-polio syndrome, symptoms such as muscle atrophy, weakness, pain and fatigue occur. It is typical that no causes for the complaints can be found during medical examinations. It is therefore suspected that post-polio syndrome is behind the complaints in some chronic diseases with no apparent cause.
Treat polio
Treatment against the polioviruses themselves is not possible, because so far there are no drugs that can be used to fight the pathogens. If the disease has broken out, only the symptoms that occur can be treated. The only effective protection against polio is the polio vaccination.
Vaccination protects against polio
Two different vaccines were available to protect against polio in Germany until 1998:
- Oral vaccination (oral polio vaccine; OPV).
- Injection (injectable polio vaccine; IPV according to Salk).
Since 1998, only the IPV vaccine is used in Germany. Although the oral vaccination, which was carried out with attenuated polioviruses, provided more effective protection, but in rare cases triggered polio itself. About one or two such cases occurred in Germany every year (vaccine poliomyelitis). Today, therefore, only the IPV vaccine is used. This vaccine cannot cause poliomyelitis because the viruses injected are not attenuated but killed.The vaccine is injected either into the buttocks, the upper arm or the thigh. The disadvantage of this form of vaccination is that it is more time-consuming and involves more costs. This makes it difficult to achieve universal vaccination coverage, especially in developing countries. Here, oral vaccination is still frequently used.
Polio – How often to vaccinate?
How often you need to be vaccinated against polio depends on the type of vaccine used – the key factor is whether a single or combination vaccine is used. As a rule, vaccinations are given at two and four months of age and between 11 and 14 months of age; an additional vaccination at three months of age is possible, depending on the vaccination schedule. In this case, the polio vaccination is often given together with the vaccinations against tetanus, diphtheria and pertussis. Between the ages of 9 and 17, a booster vaccination is recommended. If, upon looking at your immunization record, you find that you have not had all of the required polio vaccinations, you should contact your primary care physician and have the vaccinations made up.
Polio declines worldwide
Polio used to be common worldwide and occurred relatively frequently. However, the introduction of oral vaccination in 1962 has now almost completely reversed the disease. Large parts of the world are now considered polio-free. Some parents believe that there is therefore no longer any risk and no longer have their children vaccinated against polio. However, this is a dangerous fallacy. Because the lack of vaccination protection increases the risk that polio cases will occur again in Germany. Although no more cases have been reported in Germany in recent years – polio cases did occur again in Europe in 2015.
