Poliomyelitis

Causative agent

It is caused by poliovirus. Of the 3 strains of wild poliovirus (type 1, type 2, and type 3), the last case of wild poliovirus type 2 was reported in 1999 and no case of wild poliovirus type 3 has been found since the last reported case in Nigeria in November 2012. However, cases of wild poliovirus type 1 still occur in a small number of countries.

Clinical features

The disease mainly affects young children. It can cause fever, headache, vomiting, abdominal discomfort, muscle pain, stiffness in the neck and back, and paralysis. Most patients will recover, but in severe cases, it can lead to permanent disability and death.

Mode of transmission

The disease is highly infectious. It is spread from person-to-person, mainly through the faecal-oral route. The virus enters the body through oral route and finally invades the central nervous system.

Incubation period

It is usually 7 to 10 days, with a range of 4 to 35 days.

Management

Suspected infected persons should be referred to the hospital for further management and isolation. Currently, there is no curative treatment for the disease.

Since the patient’s stool may contain the virus, carers should take extra precautions in the hygiene practices when caring for the sick.

Prevention

Vaccination is the most effective way of preventing the disease. There are two types of polio vaccine: Oral Polio Vaccine (OPV) to be taken by mouth and Inactivated Polio Vaccine (IPV) to be given by injection. As OPV is known to be associated with a rare complication known as vaccine-associated paralytic poliomyelitis, IPV has been used in the Hong Kong Childhood Immunisation Programme since 2007. OPV is no longer used in Hong Kong.

On 5 May 2014, the World Health Organization (WHO) Director-General declared the international spread of poliovirus to be a Public Health Emergency of International Concern under the International Health Regulations (2005) and issued Temporary Recommendations to reduce the international spread of poliovirus. Information on the latest Temporary Recommendations of the WHO and the updated list of affected countries / states of polioviruses is available on the following website: https://polioeradication.org.

The WHO recommends that before travelling to areas with active poliovirus transmission, travellers from polio-free countries should ensure that they have completed the age-appropriate polio vaccine series, according to their respective national immunisation schedule. Adult travellers to polio-infected areas who have previously received three or more doses of OPV or IPV should also be given another one-time booster dose of polio vaccine. Travellers who have not received any polio vaccine previously should complete a primary schedule of polio vaccination before departure.

Travellers are also advised to:

• Maintain good personal and food hygiene
• Always wash hands before eating or handling food, and after going to toilet
• Avoid exposure to any potentially contaminated food or drinks

According to the WHO recommendations, countries infected with wild poliovirus or circulating VDPV (cVDPV) with potential risk of international spread should ensure/encourage that all residents and long-term visitors (i.e. > four weeks) of all ages, receive a dose of polio vaccine between four weeks and 12 months prior to international travel. Those undertaking urgent travel (i.e. within four weeks), should receive a dose of polio vaccine at least by the time of departure. Countries infected with wild poliovirus type 1, cVDPV type 1 or type 3 with potential risk of international spread should ensure such travellers to be provided with an International Certificate of Vaccination or Prophylaxis to record their polio vaccination and serve as proof of vaccination.

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