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Poliomyelitis

epidemiology of poliomyelitis its clinical Picture and ways of transmission, vaccination program

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Poliomyelitis

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  1. Poliomyelitis presentation by

  2. Poliomyelitis • A highly infectious disease, caused by any of the three serotypes of the poliovirus; Type 1, 2 & 3 • Mainly affects children under 5 years • Replicates initially in the gastrointestinal tract and in rare cases in the motor neurons of the spinal cord • Replication of the virus results in cell destruction and paralysis • Up to 95% of all polio infections are asymptomatic

  3. The virus is transmitted by person-to-person spread through the fecal-oral route • Wild polioviruses have a seasonal pattern of circulation that varies by geographic area • Suboptimal hygiene, sanitation and water quality contribute to transmission Transmission

  4. transmission • Once infected, the virus will replicate in the intestinal tract • Infected persons, with or without symptoms, will shed the virus in stools for 3-6 weeks • Previous natural infection or vaccination will reduce the extent and duration of shedding • The rate of secondary infections in susceptible households is greater than 90%

  5. clinical presentation Inapparent infection without symptoms (72%) Minor illness (24%) Transient illness characterized by several days of fever and flu-like symptoms including; malaise, drowsiness, headache, nausea, vomiting, sore throat. Nonparalytic poliomyelitis (4%) Begins as minor illness, after 1-2 days progresses to include severe headaches, stiffness and pain in the neck, back, and or limbs. This lasts 2- 10 days and recovery is usually rapid and complete. Paralytic poliomyelitis ( <1%) Characterized by minor illness for several days, then a symptom free period of 1-3 days, followed by rapid onset of flaccid-paralysis with fever and progression to the maximum extent of paralysis within a few days.

  6. The Global Polio Eradication Initiative The GPEI is a global, public-private partnership led by; • National governments • WHO • Rotary International • The US Centers for Disease Control and Prevention (CDC) • UNICEF • Bill & Melinda Gates Foundation • Gavi the Vaccine Alliance

  7. In 1988, the World Health Assembly passed a resolution to eradicate polio. At the time there were 125 endemic countries around the world and every year, more than 350,000 children were paralyzed for life by the virus. Only three countries remain endemic: Pakistan, Afghanistan and Nigeria.

  8. Significance as a Public Health Program In the absence of effective control programs using polio vaccine, paralysis develops in approximately one of every 200 children after exposure to the virus, followed in most cases by permanent disability, 5 -10% of patients with paralytic disease have a fatal outcome. If we stop current efforts, within 10 years the virus will be global and each year there could be 200,000 children that acquire permanent disability from paralytic poliomyelitis.

  9. Polio Eradication – Biological Rationale • Demonstrated feasibility of eradication • Humans are the only reservoir for poliovirus • Limited period of infectiousness • Efficacious vaccines able to interrupt transmission • Global clinical surveillance system able to detect virus

  10. THERE IS NO CURE FOR PARALYTIC POLIO, ONLY SUPPORTIVE AND SYMPTOMATIC CARE The polio vaccine, given multiple times, can protect a child for life Treatment

  11. Oral Polio Vaccine (OPV) Albert Sabin (1961) Inactivated Polio Vaccine (IPV) Jonas Salk (1955) • Delivered through oral drops • Contains live–attenuated (weakened) virus of 1, 2 or 3 poliovirus types. Monovalent (mOPV), bivalent (bOPV) or trivalent (tOPV) • OPV induces both humoral and mucosal immunity and provides individual protection against poliovirus • Shedding by the vaccinated individual can also result in passive immunity of others in close contact that were not vaccinated • It can interrupt transmission of the virus in well immunized populations • Injectable vaccine that can be administered alone or in combination with other vaccines. Requires a trained health worker • Contains inactivated virus of all three poliovirus types 1, 2 and 3 • IPV induces humoral immunity and provides individual protection against poliovirus • It does not interrupt transmission of the virus. If individuals are exposed to poliovirus they will shed the virus in stool samples • IPV can induce a higher level of mucosal and humoral immunity, when an individual is primed with OPV

  12. Poliovirus Definitions • Wild Polio Virus (WPV)is the naturally occurring poliovirus • Sabin or Sabin-likeis the weakened virus in the OPV vaccine • In under-immunized populations, the Sabin-like viruses from the OPV vaccine will continue to be transmitted from person to person. In very rare occasions the weakened virus can diverge genetically and become a Vaccine Derived Poliovirus (VDPV),regaining the ability to cause paralysis • Transmission of VDPVs, based on multiple detections of related viruses, is considered to be a circulating Vaccine Derived Poliovirus (cVDPV) • Vaccine-Associated Paralytic Poliomyelitis (VAPP)is an adverse event associated with OPV vaccination, occurring in approximately 2-4 cases per million birth cohort

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