Many of us think of polio as a disease belonging to another era. In the early 20th century, it was one of the most feared diseases in North America. Thanks to the discovery of the polio vaccine, cases haven’t been seen in Canada since 1977 and 1979 in the United States. Today, the disease is 99.9% eradicated thanks to tireless global efforts, but without total elimination it continues to be a threat in the world’s most vulnerable regions. In fact, in 2019 we saw concerning increases in polio outbreaks, with cases reported from some countries that hadn’t seen cases for decades.
So, what can we expect for 2020? In this blog, we look at polio, why outbreaks spiked in 2019, and how travellers can contribute to eradication efforts.
What is polio?
Polio is a highly infectious disease caused by the poliovirus. The virus is typically acquired through the fecal-oral route – it lives in the feces of an infected person and spreads from person-to-person through poor hygiene practices and when consuming contaminated food or water. The virus can also spread through respiratory droplets when coming into close contact with an infected person who coughs or sneezes.
Polio infection typically results in a mild illness that causes symptoms such as fever, headache, nausea, and muscle stiffness and pain. In rare cases, polio infection can cause major illness that affects the central nervous system and can lead to life-long paralysis, and in some cases death.
Types of polioviruses
Polio infections can be classified as wild poliovirus (WPV) or vaccine-derived poliovirus (VDPV).
Wild poliovirus refers to the virus when it naturally occurs and circulates in the environment. Wild polio can be prevented through two effective vaccines: The oral polio vaccine (OPV) and the inactivated polio vaccine (IPV). The oral polio vaccine contains a weakened live version of the virus, whereas the inactivated polio vaccine (IPV), an injectable vaccine, does not contain live virus.
The oral polio vaccine is used in many countries and has been instrumental towards global efforts to eradicate the disease. However, sometimes when an individual receives the oral polio vaccine, the virus can cause illness if it mutates from the original strain used in the vaccine. This is known as vaccine-derived poliovirus. When the mutated virus is shed into the environment, it can regain its ability to cause illness and paralysis over time as it passes from one non-immune person to the next. This is referred to as circulating vaccine-derived poliovirus (cVDPV) and it occurs in regions where there is low vaccination coverage, meaning many people are susceptible to the virus or not fully immune. Poor sanitary conditions such as contaminated water sources and inadequate sewage systems also fuel its spread.
The ongoing fight
There is still a long way to go towards eradicating polio completely. Part of what has made polio so difficult to eradicate over the years was the presence of different strains (type 1, 2, and 3). Although wild poliovirus types 2 and 3 have been eradicated, WPV1 is still endemic (regularly found) in Afghanistan and Pakistan.
In 2019, 163 cases of wild poliovirus type 1 were reported – 28 from Afghanistan and 135 from Pakistan. Unfortunately, control efforts have been challenging due to instability in Afghanistan and widespread misinformation about the vaccine in Pakistan, resulting in many communities and individuals being unvaccinated. As of August 2019, Nigeria reached 3 years without reporting a case and may be certified polio-free this year.
In 2019 we also saw a significant increase in circulating vaccine-derived poliovirus cases. Outbreaks were reported in 16 countries across Africa, the Eastern Mediterranean, Southeast Asia, and the Western Pacific. In several countries, outbreaks were reported for the first time in years. For example, prior to 2019 the Philippines hadn’t seen a polio case for 19 years; it reemerged as a result of the country’s deteriorated health system, gaps in vaccination coverage, and poor sanitation conditions.
A World Health Organization Emergency Committee, which met in December 2019, expressed concern that the trend of increasing cases does not appear to be slowing. It reiterated that polio continues to be a Public Health Emergency of International Concern (PHEIC).
Only humans can carry and transmit polio, so everyone needs to be fully vaccinated for the disease to be eradicated. As such, all travellers need to do their part to ensure they are appropriately protected and prevent polio from spreading.
Should I get vaccinated?
Wherever you travel, you should ensure you are up-to-date with all of your routine immunizations, including polio. Make sure you have been fully vaccinated. A primary vaccination series is necessary for those not previously or only partially vaccinated.
Depending on your itinerary, proof of Polio may be required or a booster dose may be recommended:
Polio vaccination required
To prevent the spread of polio, some countries require specific travellers to provide proof of vaccination (an International Certificate of Vaccination or Prophylaxis – yellow card) upon arrival. In many cases, this requirement only applies to travellers arriving from polio-endemic countries like Afghanistan, Nigeria, and Pakistan or countries with ongoing outbreaks. You can see a full list of countries that require proof of polio vaccination and their requirements here.
Polio vaccination recommended
Travellers going to at-risk countries for 4 weeks or more should receive a booster dose of polio vaccine between 4 weeks and 12 months prior to travel. A booster dose will provide life-long immunity to the virus. Countries at risk are those with a history of the disease and low vaccination rates such as Ukraine, Madagascar, and Guinea. You can see a full list of countries considered at risk of polio transmission here.
Travellers going to countries with recent (past 12 months) or active outbreaks of wild or circulating vaccine-derived polio (such as Pakistan and the Philippines) should also receive a booster dose before their trip. Consider carrying documentation of your polio vaccines to provide proof of immunity if needed.
Other ways to prevent the spread of polio
In addition to being fully vaccinated against polio, travellers should practice good personal hygiene and follow food and water safety precautions. Check out Food and Water Safety and Hand Hygiene for helpful tips and advice.
For additional information on polio and ongoing outbreaks, check out the Global Polio Eradication Initiative (GPEI).
Image by Tony Lam Hoang, Unsplash.
Article by Claire Westmacott and Phoebe To