Polio (Human)
Primary reference(s)
WHO, 2019. Poliomyelitis. World Health Organization (WHO). Accessed 16 December 2019.
Additional scientific description
Poliomyelitis (polio) is a highly infectious viral disease that largely affects children under 5 years of age. The virus is transmitted by person-to-person spread mainly through the faecal-oral route or, less frequently, by a common vehicle (e.g., contaminated water or food) and multiplies in the intestine, from where it can invade the nervous system and cause paralysis (WHO, 2019).
Polio virus infection is mostly asymptomatic. If there are symptoms these can include fever, malaise, sore throat, anorexia, myalgia, headache, and in less than 1% of infected children illness can progress to paralytic disease. Typically, the paralysis is acute onset and flaccid in nature and asymmetrically involving limbs. One in 200 infections leads to irreversible paralysis. Among those paralysed, 5% to 10% may die due to respiratory paralysis. If the child recovers, paralysis is often permanent (WHO, 2019).
Polio is diagnosed clinically through symptoms and laboratory methods including virus isolation in stool, serological testing and analysis of cerebrospinal fluid (Kasper and Fauci, 2013; WHO, 2019).
Cases due to wild poliovirus have decreased by over 99% since 1988, from an estimated 350,000 cases then, to 33 reported cases in 2018 (WHO, 2019).
There is no cure for polio, but vaccination is highly effective in preventing the disease (WHO, 2019).
Metrics and numeric limits
Polio is targeted for global eradication and since 2017, only two countries (Afghanistan and Pakistan) have detected wild polio transmission. However, in recent years there has been a resurgence of vaccine derived poliovirus (VDPV). This emerges in areas where poor vaccination coverage allows the attenuated vaccine virus to circulate and revert to a pathogenic form due to genetic mutation (GPEI, 2016, 2019).
Key relevant UN convention / multilateral treaty
International Health Regulations (2005), 3rd ed. (WHO, 2016).
Examples of drivers, outcomes and risk management
Polio infection is more common in socioeconomically disadvantaged areas, especially in those where conditions are crowded and in tropical areas where hygiene is poor (WHO, 2019).
Conflict and insecurity coupled with fragile health systems are risk factors for ongoing polio transmission particularly when these factors result in children being missed by vaccination programmes due to inaccessibility (WHO, no date).
References
GPEI, 2016. Classification and reporting of vaccine-derived polioviruses (VDPV). Global Polio Eradication Initiative (GPEI). Accessed 13 September 2020.
GPEI, 2019. Initiative Polio Endgame Strategy 2019-2023. Global Polio Eradication Initiative (GPEI). Accessed 16 December 2019.
Kasper, D. and A. Fauci, 2013. Harrison’s Infectious Diseases, 2nd Ed. McGraw-Hill Education.
WHO, no date. Building peace in fragile and conflict settings through health. World Health Organization (WHO). Accessed 8 April 2021.
WHO, 2016. International Health Regulations (2005), 3rd ed. World Health Organization (WHO). Accessed 26 September 2020.
WHO, 2019. Poliomyelitis. World Health Organization (WHO). Accessed 16 December 2019.