epidemiology of poliomyelitis ashry gad mohamed mbchb, mph, drph prof. of epidemiology
DESCRIPTION
Epidemiology of Poliomyelitis Ashry Gad Mohamed MBchB, MPH, DrPH Prof. of Epidemiology Medical College, KSU. First described by Michael Underwood in 1789 Polio = grey & Myelitis =marrow (spinal cord) & Itis = inflamation Spectrum 95% asymptomatic. - PowerPoint PPT PresentationTRANSCRIPT
Epidemiology of Poliomyelitis
Ashry Gad MohamedMBchB, MPH, DrPH
Prof. of EpidemiologyMedical College, KSU
• First described by Michael Underwood in 1789
• Polio = grey & Myelitis =marrow (spinal cord) & Itis = inflamation
• Spectrum
95% asymptomatic.
4-8% minor non-specific illness (URTI, GIT, influenza like)
1-2% Non paralytic aseptic meningitis.
1% Flaccid paralysis
0 20 40 60 80 100
Percent
Asymptomatic Minor non-CNS illness
Aseptic menigitis Paralytic
Outcomes of poliovirus infection
Flaccid paralysis
• Asymmetrical.
• Affect large muscles.
• No sensory loss.
• No changes in recognation.
• 80% spinal, 19% bulbospinal & 1-2% bulbar
• Mortality:
2-5% children
15-30% adults
25-75% bulbar type
Polio Eradication• Before 1979 whole world
• Last case in United States in 1979
• Western Hemisphere certified polio free in 1994
• 1988 350.000
• 2001 483
• 2003 784
• 2006 1999
• 2007 673
Level 2009 2010
Globally 1606 874
Endemic countries 1256 211
Non endemic countries
350 663
Country 2009 2010
Pakistan 89 134
Afphanistan 38 23
Mauritania 13 5
India 741 41
Chad 64 18
Nigeria 388 13
Congo 3 75
Sudan 45 -
Angola 29 30
Russia 0 14
Wild Poliovirus 1988
Poliomyelitis 2004
Poliovirus
• Enterovirus (RNA)
• Three serotypes: 1, 2, 3
• Minimal heterotypic immunity between serotypes
• Rapidly inactivated by heat, formaldehyde, chlorine, ultraviolet light
Poliomyelitis Pathogenesis
• Entry into mouth
• Replication in pharynx, GI tract, local lymphatics
• Hematologic spread to lymphatics and central nervous system
• Viral spread along nerve fibers
• Destruction of motor neurons
Poliovirus Epidemiology
• Reservoir Human
• Transmission Fecal-oral Oral-oral possible
• Communicability 7-10 days before onset Virus present in stool 3-6 weeks
Poliovirus Vaccine
• 1955 Inactivated vaccine
• 1961 Types 1 and 2 monovalent OPV
• 1962 Type 3 monovalent OPV
• 1963 Trivalent OPV
• 1987 Enhanced-potency IPV (IPV)
Inactivated Polio Vaccine
• Contains 3 serotypes of vaccine virus
• Grown on monkey kidney (Vero) cells
• Inactivated with formaldehyde
• Contains 2-phenoxyethanol, neomycin, streptomycin, polymyxin B
Oral Polio Vaccine
• Contains 3 serotypes of vaccine virus
• Grown on monkey kidney (Vero) cells
• Contains neomycin and streptomycin
• Shed in stool for up to 6 weeks following vaccination
Inactivated Polio Vaccine
• Highly effective in producing immunity to poliovirus
• >90% immune after 2 doses
• >99% immune after 3 doses
• Duration of immunity not known with certainty
Oral Polio Vaccine
• Highly effective in producing immunity to poliovirus
• 50% immune after 1 dose
• >95% immune after 3 doses
• Immunity probably lifelong
Polio Vaccine Adverse Reactions
• Rare local reactions (IPV)
• Vaccine associated paralytic poliomyelitis (OPV)
Vaccine-Associated Paralytic Polio
• Increased risk in persons >18 years
• Increased risk in persons with immunodeficiency
• No procedure available for identifying persons at risk of paralytic disease
• 5-10 cases per year with exclusive use of OPV
• Most cases in healthy children and their household contacts
Vaccine-Associated Paralytic Polio (VAPP) 1980-1998
• Healthy recipients of OPV 41%
• Healthy contacts of OPV recipients 31%
• Community acquired 5%
• Immunodeficient 24%
Polio VaccineContraindications and Precautions
• Severe allergic reaction to a vaccine component or following a prior dose of vaccine
• Moderate or severe acute illness
Global Polio Eradication Initiative
Objectives:
1-To interrupt transmission of the wild poliovirus ASAP.
2-To achieve certification of global polio eradication.
3-To contribute to health systems development and strengthening routine immunization and surveillance for communicable diseases in a systematic way.
Global Polio Eradication Initiative
Strategies:1.high infant immunization coverage with four doses
of oral poliovirus vaccine (OPV) in the first year of life;
2.supplementary doses of OPV to all children under five years of age during SIAs;
3.surveillance for wild poliovirus through reporting and laboratory testing of all acute flaccid paralysis (AFP) cases among children under fifteen years of age;
4.targeted “mop-up” campaigns once wild poliovirus transmission is limited to a specific focal area
Global Polio Eradication Initiative
Before a WHO region can be certified polio-free, three conditions must be satisfied:
1.there are at least three years of zero polio cases due to wild poliovirus;
2.disease surveillance efforts in countries meet international standards; and
3.each country must illustrate the capacity to detect, report and respond to “imported” polio cases
Poliomyelitis surveillance
• Acute flaccid paralysis All cases of acute flaccid pralysis among
children younger than 15 years and all cases of suspected polio in any person at any age.
• Performance indicators:
1. Completeness of reporting (80% at least).
2. Sensitivity of surveillance (1/100,000).
3. Completeness of case investigation (80% adequate stool specimen).
4. Complete follow up (80% 60 days).
5. Lab investigation of all cases in WHO ref. lab.
The most important aspect of this classification is the collection of 2 adequate stool samples from all cases. Samples are considered adequate if both the specimens (1) are collected within 14 days of paralysis onset and at least 24 hours apart; (2) are of adequate volume (8-10g) and (3) arrives at a WHO-accredited laboratory in good condition (ie, no desiccation, no leakage), with adequate documentation and evidence of cold-chain maintenance
References1-http://www.emro.who.int/PolioFax/
2-http://www.who.int/topics/poliomyelitis/en/
3-http://healthcare.utah.edu/healthinfo/adult/infectious/polio.htm
4- Control of communicable diseases in man, manual. APHA 2005.