Polio is a highly infectious disease caused by the poliovirus types 1, 2 and 3. Polio infection occurs in the gastrointestinal tract and may spread to the lymph nodes. In rare cases, it can spread to the central nervious system and cause paralysis. 

The disease manifestation can range from inapparent infection to severe paralysis. Over 90% of infections have no symptoms or result in slight fever, while about 10% present with common symptoms including fever, tiredness, headache, nausea and vomiting. Paralysis occurs in less than 1% of infections.

Three forms of paralytic polio may be seen:

a) Spinal paralytic polio
Patients would first experience ‘minor’ illness with symptoms such as fever, muscle pain, nausea, vomiting and stiff neck/back. This lasts for 1 to 3 days and is followed by a symptom-free period of 1 to 5 days before onset of paralysis. Paralysis varies from single muscle involvement to affliction of all four limbs. Despite the paralysis, there is no accompanying sensory loss.

b) Bulbar paralytic polio (5 to 35% of paralytic cases of polio)
This causes paralysis of the soft palate, pharynx and larynx resulting in difficulty in swallowing and breathing.

c) Polioencephalitis (uncommon, occurs mainly in infants)
This manifests as confusion, sensory changes and seizures.

The incubation period lasts between 7 to 14 days and the patient is infectious a few days before and after the onset of the disease. The disease is spread from person-to-person mainly via faecal-oral route [faecal-oral route means that the organisms (e.g. virus or bacteria) are transmitted via faeces of one host to the mouth of another] or less commonly through respiratory droplet transmission. 

There is no specific therapy for polio. Management is supportive and symptomatic. 

Polioviruses can usually be isolated from the throat swab in the first week of illness. Stool cultures for the virus may remain positive for several weeks.

Two types of vaccine are available: an injectable inactivated polio vaccine (IPV) and an oral live, attenuated polio vaccine (OPV).

In Singapore, polio vaccine has been administered routinely in the National Childhood Immunisation Programme since 1962. The primary course is given at 3, 4 and 5 months while boosters are given at 18 months, 6+ years and 10+ years. Young babies are also protected by their mother's antibodies for a short period of time.

Adults should ensure that they have received at least three doses of polio vaccine in the past. If this is not the case, ‘catch-up’ immunisation should be arranged with your doctor at the following intervals:

- The first dose at any time;
- The second dose 1 to 2 months later; and
- The third dose 6 to 12 months after the second dose.

In an unvaccinated adult who has never received polio vaccine:
 
- The first and second dose should be given as IPV; and
- The third dose may be given as OPV or IPV.

If the protection is required within shorter intervals, accelerated immunisation schedules can be used for unimmunised children and adults with the following intervals:

- If more than 8 weeks are available before protection is needed, three doses should be administered at least 4 weeks apart.
- If fewer than 8 weeks but more than 4 weeks are available before protection is needed, two doses should be administered at least 4 weeks apart.
- If fewer than 4 weeks are available before protection is needed, a single dose is recommended.

The remaining doses of vaccine should be administered later, at the recommended intervals, if the person remains at increased risk for exposure to poliovirus.

One booster dose of the polio vaccine is recommended for adults (18 years and above) who have had at least three doses of the polio vaccine only if they are at risk of polio. These include:

- Travellers to countries with on-going or recent polio transmission^
- Healthcare workers in possible contact with persons with polio
- Laboratory workers who may handle polio viruses

Based on available information, adults do not need more than a single lifetime booster dose. Please consult your doctor for more advice and information on vaccination against polio.

^Please refer to Polio Eradication website for the latest list of countries with ongoing or recent transmission of polio.

The polio vaccine is available at polyclinics, private clinics as well as travellers' clinics.  

Polio immunisation has been routinely administered in the National Childhood Immunisation Programme since 1962. You should check your personal immunisation records and if in doubt, consult your doctor for advice on whether you would require repeat immunisation. The National Immunisation Registry (NIR), under Health Promotion Board maintains immunisation records of children from birth to 18 years of age in Singapore. Records for children born on or after 1 January 1996 are available online on NIR website.

You should ensure that you have received at least three doses of polio vaccine in the past prior to your travel. Booster dose of the polio vaccine is recommended for adults who have had at least three doses of the polio vaccine and are travelling to countries with ongoing or recent transmission of polio. In addition, you should continue to observe good personal and food hygiene practices.

If you develop symptoms of fever, muscle pain, nausea, vomiting and stiff neck/back within two weeks of your return, please see your doctor immediately and inform him or her of your travel history.

There is no need to be alarmed as the risk of polio in Singapore is very low due to a high level of immunity in the population.  

Singapore has not had a local case of polio since 1973. This is due to our successful immunisation programme against polio.

Singapore is certified by the World Health Organization as a polio-free country. Nevertheless, the Ministry of Health remains vigilant and maintains a comprehensive system of notification and epidemiological surveillance to guard against possible importation of poliovirus. The high level of polio immunisation among the residents also ensures that the population is adequately protected against any importation of poliovirus.