Poliomyelitis (polio)

While the global health community is now close to eradicating poliomyelitis (often referred to as polio) worldwide, this objective has not yet been achieved. As a result, polio vaccinations are still required in countries now free of the disease; and booster vaccinations in adulthood may also be recommended before travel to certain destinations.

Switzerland has been officially polio-free since the beginning of the 1990s. But as long as population groups remain around the globe who are not or are inadequately vaccinated, and as long as poliomyelitis has not been entirely eradicated worldwide, there is still a risk of the poliovirus returning to regions from which it has already been eliminated.

The recent case of poliomyelitis in New York state (USA) and the identification of the poliovirus in waste water in several countries show how vitally important it still is that all residents of Switzerland are fully vaccinated against polio as recommended under the Swiss Vaccination Plan, which can be accessed (in German) here (French and Italian versions are also available).

Travellers should also find out whether they may need a polio booster vaccination in advance of their journey at the www.healthytravel.ch website.

Full vaccination against poliomyelitis (see ‘Prevention’ below) provides very effective protection against the disease.

Pathogen and transmission

Poliomyelitis is caused by the poliovirus. Of the three virus types, Type 2 is now very rarely found. Some cases of the disease are also caused by circulating derivatives of polio vaccine strains.

At the start of the infection, the poliovirus is excreted for about a week via nose and throat secretions. After this the virus is excreted through the infected person’s stools for a further three to six weeks. So most person-to-person transmissions of the virus occur via smear infection – from dirty hands or contaminated water or food – or through droplets emitted from the throat of an infected person. By the time poliomyelitis is diagnosed, almost all the persons who have been in close contact with the patient and are not vaccinated against the disease will also have become infected.

Pathology

For 90 per cent of infected persons, a poliovirus infection will cause no symptoms at all. Among those who do fall ill, the disease will produce flu-like symptoms or gastrointestinal pain.

Fewer than one per cent of infected persons develop the classic polio signs of flaccid paralysis (which usually occurs on one side of the body, and in the legs more than the arms). Respiratory paralysis may also develop in some rare cases. Recovery from flaccid paralysis ranges all the way from full recovery to life-long paralysis.

There is no antiviral treatment for polio: only the symptoms can be eased. Persons who have been infected may also experience post-polio syndrome, with pains and muscle weakening, years or even decades later in life.

Given the rareness of the disease today, any isolated case of possible poliomyelitis is more likely to have been caused by other pathogens, toxins or other (immunological or genetic) factors. This is important in epidemiological monitoring terms: the identification of any such cases of flaccid paralysis points to a well-functioning monitoring and reporting system.

Distribution and frequency of occurrence

The World Health Organization (WHO) resolved in 1988 to eradicate poliomyelitis worldwide. Three WHO Regions are currently considered free of wild poliovirus: the Americas, the Western Pacific and Europe.

Polio was still endemic in Afghanistan and Pakistan, in 2024. Mutated derivatives of vaccine strains have been responsible for several hundred polio cases since 2000. These viruses are largely present in regions with low routine vaccination coverage.

The last case of poliomyelitis caused by wild poliovirus in Switzerland was in 1982.

Prevention

Vaccination is the only way to protect people from this disease. Given the constant risk that the poliovirus could be brought back into a currently polio-free zone, it is vitally important that all infants and other unvaccinated persons are protected through vaccination, and that such vaccination protection remains assured by the administration of all the booster vaccinations required.

• Infants should receive three doses of the vaccine at 2, 4 and 12 months, followed by a final dose between the ages of 4 and 7.
• Unvaccinated adults should receive three doses, with the second and third doses administered 2 and 8 months respectively after the first.
• A booster vaccination may be advisable for both children and adults after ten years – for persons at greater risk of infection due to their work, for instance, or those spending an extended time in regions where the poliovirus continues to circulate (see also the www.healthytravel.ch website).

Further information

• Documents

  Further relevant documents are available in German, French and Italian

• Links

  Healthytravel: medical advice for travellers

  Swiss Vaccination Plan 
  (Page available only in German, French and Italian)

  Swiss cantonal vaccination coverage monitoring
  (Page available only in German, French and Italian)

Further topics