Poliomyelitis

Poliomyelitis

Authors: Doctors David L. Heymann1 and R. Bruce Aylward Creation date: August 2004

Scientific Editor: Professor Hermann Feldmeier

1Polio Eradication Initiative WHO, Geneva 1211, Switzerland. [email protected]

Abstract Key-words Disease name/ synonyms Definition/diagnostic criteria Differential Diagnosis Etiology Clinical description Diagnostic methods Epidemiology Management/treatment Unresolved questions References

Abstract Poliomyelitis is a viral infection caused by any of three serotypes of human poliovirus and is most often recognized by the acute onset of flaccid paralysis. It affects primarily children under the age of 5 years. Transmission is primarily person-to-person spread, principally through the fecal-oral route. Usually the infection is limited to the gastrointestinal tract and nasopharynx, and is often asymptomatic. The central nervous system, primarily the spinal cord, may be affected, leading to rapidly progressive paralysis. Motor neurons are primarily affected. Encephalitis may also occur. The virus replicates in the nervous system, and may cause significant neuronal loss, most notably in the spinal cord. Poliomyelitis must be distinguished from other paralytic conditions by isolation of virus from stool. Prevention is the only cure for paralytic poliomyelitis. Both inactivated polio vaccine (IPV) and oral polio vaccine (OPV) are commercially available. Progress in poliomyelitis eradication since its beginning in 1988 has been remarkable. In 1988, 125 countries were endemic for polio and an estimated 1,000 children were being paralyzed each day by wild poliovirus. By the end of 2003, six polio-endemic countries remained (Afghanistan, Egypt, India, Niger, Nigeria, Pakistan), and less than 3 children per day were being paralyzed by the poliovirus. Interruption of human transmission of wild poliovirus worldwide is now targeted for the end of 2004.

Key-words Poliomyelitis, acute flaccid paralysis, inactivated polio vaccine (IPV), oral polio vaccine (OPV)

Disease name/ synonyms central nervous system. Flaccid paralysis occurs Acute poliomyelitis, Polio, Polioviral Fever, in less than 1% of poliovirus infections; aseptic Infantile Paralysis meningitis in another 1%; a minor illness with symptoms including fever, malaise, headache, Definition/diagnostic criteria nausea and vomiting in a further 10%, and the Poliomyelitis is a viral infection most often remaining 88% of infections are asymptomatic. recognized by the acute onset of flaccid paralysis. Poliovirus infection occurs in the Differential Diagnosis gastrointestinal tract with spread to the regional The most frequent cause of acute flaccid lymph nodes and, in a minority of cases, to the paralysis (AFP) that must be distinguished from

Heymann D and Aylward B. Poliomyelitis. Orphanet Encyclopedia. August 2004. http://www.orpha.net/data/patho/GB/uk-Poliomyelitis.pdf 1 poliomyelitis is Guillain-Barré syndrome (GBS). cause an illness simulating paralytic Paralysis in GBS is typically symmetrical and poliomyelitis. Definitive laboratory diagnosis may progress for periods as long as 10 days. requires isolation of the wild poliovirus from stool The fever, headache, nausea, vomiting and samples, CSF or oropharyngeal secretions in pleocytosis characteristic of poliomyelitis are cell culture systems of human or monkey origin usually absent in GBS; high protein and low cell (primate cells). Specialized laboratories can counts in the cerebrospinal fluid (CSF) and differentiate “wild” virus strains from vaccine sensory changes are seen in the majority of virus strains. GBS cases. Other causes of AFP include transverse myelitis, Epidemiology traumatic neuritis, infectious and toxic Accurate data on polio case counts are available neuropathies, tick paralysis, myasthenia gravis, for 1996 to date from the World Health porphyria, botulism, insecticide poisoning, Organization (WHO) website. As a result of polymyositis, trichinosis, central nervous system improved immunization worldwide and the global schistosomiasis and periodic paralysis. initiative to eradicate poliomyelitis, the disease Differential diagnosis of acute nonparalytic may be on the verge of worldwide eradication; 6 poliomyelitis also includes other forms of acute countries remain endemic at mid-2004 nonbacterial meningitis, purulent meningitis, (Afghanistan, Egypt, India, Niger, Nigeria, brain abscess, tuberculous meningitis, Pakistan) with 440 cases reported to date. leptospirosis, lymphocytic choriomeningitis, Although wild poliovirus transmission has infectious mononucleosis, the encephalitides, ceased in the majority of countries, importation neurosyphilis and toxic encephalopathies. remains a threat. A large outbreak of poliomyelitis occurred in 1992–1993 in the Etiology Netherlands among members of a religious Poliomyelitis is caused by any of the three group that refuse immunization. The virus was serotypes of human Poliovirus (genus also found among members of a related religious Enterovirus). Type 1 is isolated from paralytic group in Canada, although no cases occurred. cases most often and type 3 less so. Circulating Polio-free countries remain at risk of polio as wild type 2 poliovirus has not been detected long as the wild poliovirus continues to transmit since October 1999. Type 1 most frequently from human to human; countries that do not causes epidemics. maintain high immunity levels among all segments of population are at greatest risk. Clinical description Historically, in endemic areas, cases of Usually the infection is limited to the poliomyelitis occurred both sporadically and as gastrointestinal tract and nasopharynx, and is epidemics each year in tropical countries during often asymptomatic. The central nervous the rainy season. Poliomyelitis is today primarily system, primarily the spinal cord, may be a disease of infants and children under the age affected, leading to rapidly progressive paralysis. of five years. Motor neurons are primarily affected. Transmission is primarily person-to-person Encephalitis may also occur. The virus replicates spread, principally through the fecal-oral route. in the nervous system, and may cause In rare instances, milk, foodstuffs and other significant neuronal loss, most notably in the materials contaminated with feces have been spinal cord. incriminated as vehicles; water and sewage are The paralysis of poliomyelitis is usually rarely implicated. The period of incubation is asymmetric, with fever present at the onset. The commonly 7–14 days for paralytic cases. Virus maximum extent of paralysis is reached in a typically persists in the throat for approximately 1 short period, usually within 3–4 days. The site of week and in feces for 3–6 weeks after infection, paralysis depends on the location of nerve cell with transmission greatest during the days destruction in the spinal cord or brain stem. The before and after onset of symptoms. legs are affected more often than the arms. Type-specific immunity, apparently of lifelong Paralysis of the respiration and/or swallowing duration, follows both clinically recognizable and muscles can be life-threatening. Some unapparent infections. Intramuscular injections, improvement in paralysis may occur during trauma or surgery during the incubation period or convalescence, but paralysis still present after prodromal illness may provoke paralysis in the 60 days is likely to be permanent. affected extremity.

Diagnostic methods Management/treatment Poliomyelitis must be distinguished from other Prevention is the only cure for paralytic paralytic conditions by isolation of virus from poliomyelitis. Both a trivalent live, attenuated stool. Other enteroviruses (notably types 70 and oral poliovirus vaccine (OPV) and an injectable, 71), echoviruses and coxsackieviruses can inactivated poliovirus vaccine (IPV) are

Heymann D and Aylward B. Poliomyelitis. Orphanet Encyclopedia. August 2004. http://www.orpha.net/data/patho/GB/uk-Poliomyelitis.pdf 2 commercially available. OPV simulates natural References infection by inducing both circulating antibody Circulating Vaccine-Derived Poliovirus-- and resistance to infection of the pharynx and Philippines, Morbidity and mortality weekly intestine, and also immunizes some susceptible report, 2001, 50:874–5. contacts through secondary spread. WHO Expanded Programme on Immunization. Field recommends the use of OPV alone for guide for supplemental activities aimed at immunization programs in developing countries achieving polio eradication. WHO/EPI/GEN 95.1. because of its superior capacity to provide Heymann DL, Rodier GR. Hot spots in a wired population immunity through community spread. world. Lancet Infectious Diseases 2001, 1: 345- IPV likewise provides excellent individual 353. protection by inducing circulating antibody that Kew OM, Morris-Glasgow V, Landaverde M, blocks the spread of virus to the CNS. IPV does Burns C, Shaw J. et al. Outbreak of poliomyelitis not induce intestinal immunity of the level in Hispaniola associated with circulating type 1 induced by OPV. vaccine-derived poliovirus. Science 2002, 296: There are no risks associated with IPV. OPV, 356-359. however, is associated with two risks: vaccine- Kew OM, Wright PE, Agol VL, Delpeyroux F, et related paralytic polio (VAPP) and outbreaks al. Circulating vaccine-derived polioviruses: caused by circulating vaccine-derived poliovirus current knowledge. Bulletin of the World Health (cVDPV). VAPP occurs in vaccine recipients or Organization, 2004, 82:1:16-23 their healthy contacts at a rate of approximately Mulders MN, Reimerink JHJ, Koopmans MPG, one in every 800 000 first vaccinations. van Loon AM, van der Avoort HGAM. Genetic Circulating VDPV are recombinants with other analysis of wild type poliovirus importation into neurovirulent enteric viruses capable of the Netherlands (1979-1995). Journal of spreading through populations. The extent of the Infectious Diseases 1997;176:617-24. cVDPV problem is currently being evaluated. Rousset D et al. Recombinant vaccine-derived There is no curative antiviral for poliomyelitis. poliovirus in Madagascar. Emerging Infectious Treatment during acute illness is for the Diseases, 2003, 9:885–887. complications of paralysis and requires expert Smith J, Leke R, Adams A, Tangermann RH. knowledge and equipment, especially for Certification of polio eradication:process and patients in need of respiratory assistance. lessons learned. Bulletin of the World Health Physical therapy is used to attain maximum Organization, 2004, 82:1:24-29. function after paralytic poliomyelitis and can WHO global action plan for laboratory prevent many deformities that are late containment of wild polioviruses. Second manifestations of the illness. Edition. WHO/V&B/03.11. World Health Organization. Guidelines for the Unresolved questions safe production and quality control of IPV Infrequently, recurrence of muscle weakness manufactured from wild polioviruses. Geneva: following recovery may occur many years after World Health Organization; (in press) for latest the original infection has resolved (“postpolio publication information visit: syndrome”); this is not believed to be related to http://www.who.int/biologicals persistence of the virus itself, but little is known Yang C-F et al. Circulation of endemic type 2 of the biological mechanism that causes this vaccine-derived poliovirus in Egypt from 1983 to syndrome. 1993. Journal of virology, 2003, 77:8366–8377.

Heymann D and Aylward B. Poliomyelitis. Orphanet Encyclopedia. August 2004. http://www.orpha.net/data/patho/GB/uk-Poliomyelitis.pdf 3