Polio disease ujsn3 iksnuss. Isnnej.pptx

Izisn

1. Polio disease Sem-5-501 Unit-3

2. Contenet Introduction & Background Virology of Poliovirus Epidemiology Clinical Manifestations Diagnostic Tools Vaccine Development History Global Eradication Initiatives Challenges in Polio Eradication Case Studies or Recent Data

3. History of Polio The disease has been known since ancient times — with cases recorded in Egyptian carvings showing withered limbs. Virus Identified: The poliovirus was identified in 1908 by Karl Landsteiner and Erwin Popper. Major Outbreaks: In the early 1900s, industrialized nations began experiencing devastating outbreaks , especially during summer months, earning it the name " infantile paralysis ." Public Fear: By the mid-20th century, polio was one of the most feared diseases in the world, particularly in the U.S. and Europe.

4. What is polio? Polio , short for poliomyelitis , is a highly infectious viral disease caused by the poliovirus , which primarily affects young children under the age of 5 . In severe cases, the virus invades the nervous system and can cause irreversible paralysis —usually in the legs, and sometimes even affecting the muscles that control breathing or swallowing. Nature of the Virus Causative Agent: Poliovirus , a member of the Enterovirus C species in the Picornaviridae family. Types of Poliovirus: Type 1 (PV1) – most common and most virulent Type 2 (PV2) – declared eradicated in 2015 Type 3 (PV3) – declared eradicated in 2019 The virus spreads person-to-person , especially via the fecal-oral route , and less commonly through contaminated food or water.

5. Virology of polio virus 1. Classification of Poliovirus Family: Picornaviridae Genus: Enterovirus Species: Enterovirus C Virus Type: Small, non-enveloped , positive-sense single-stranded RNA ( ssRNA ) virus 2.Structure of Poliovirus Size: ~27 nanometers in diameter (very small) Capsid : Icosahedral shape made of 4 structural proteins (VP1–VP4) VP1 is responsible for host cell receptor binding VP4 is located internally and stabilizes the capsid Envelope: Poliovirus is non-enveloped , making it more resistant to detergents, alcohol, and environmental stress.

6. 3. Genome Type: Single-stranded, positive-sense RNA (~7,500 nucleotides) Genome Functions: Acts as mRNA upon entry into the host cell Translates into a single large polyprotein , which is then cleaved into structural and non-structural proteins 4. Replication Cycle Attachment: Poliovirus binds to the CD155 receptor (poliovirus receptor, PVR) on human epithelial cells, especially in the oropharynx and intestines. Entry: The virus is internalized via receptor-mediated endocytosis . Uncoating : The viral RNA is released into the cytoplasm. Translation: The RNA is translated into a single polyprotein . Polyprotein Cleavage: Viral proteases (2A, 3C) cleave the polyprotein into: Structural proteins (VP1–VP4) Nonstructural proteins (e.g., RNA-dependent RNA polymerase) RNA Replication: The viral RNA is replicated through a negative-sense intermediate. Assembly: New virions are assembled in the cytoplasm. Release: Host cells are lysed , releasing thousands of new virions .

7. 5. Pathogenesis Primary Replication Site: Oropharynx and gastrointestinal tract Secondary Spread: Virus can enter the bloodstream and, in rare cases, cross the blood–brain barrier or spread via peripheral nerves to the central nervous system (CNS) Neurotropism : Poliovirus shows preference for motor neurons in the anterior horn of the spinal cord , leading to flaccid paralysis. 6. Types of Poliovirus (Serotypes) Type 1 – Most virulent and responsible for most cases of paralysis Type 2 – Eradicated globally in 2015 Type 3 – Eradicated in 2019

8. Epidemiology Epidemiology of polio refers to the study of the distribution, patterns, causes, and control of poliovirus infection in human populations. 1. Global Distribution & Burden (Historical) Pre-vaccine era (before 1955): Polio caused frequent epidemics , particularly in high-income countries. Peak incidence in children under 5 years old , especially during summer . Paralytic polio affected tens of thousands of children annually. Post-vaccine era: With the introduction of IPV and OPV, polio cases plummeted globally . From 350,000+ cases in 1988 , to fewer than 200 per year globally in the 2020s. 2. Transmission Dynamics Factor Detail Reservoir - Humans (no animal reservoir) Mode of Transmission - Fecal–oral route; less commonly, oral–oral Infectious Period - Typically 7–10 days before and after onset of symptoms Incubation Period -7–21 days (can range from 3–35 days) Basic Reproduction Number (R₀) -Estimated between 5 and 7 for wild poliovirus in non-immune populations

9. 3. Risk Factors Age: Primarily affects children under 5 Geographic regions: Higher risk in areas with: Low vaccine coverage Poor sanitation and hygiene Conflict zones: Political instability disrupts vaccination and surveillance efforts Migration: Movement of people from endemic to polio-free regions can cause outbreaks. 4. Current Status of Polio Region Status Africa Certified polio-free in 2020 (wild poliovirus) South Asia Endemic in Afghanistan and Pakistan Rest of world Free from wild polio, but occasional outbreaks of vaccine-derived poliovirus ( cVDPV ) occur in under-immunized areas

10. 5. Types of Poliovirus Cases Wild Poliovirus (WPV): Caused by naturally occurring poliovirus types Only WPV1 remains in circulation Vaccine-Derived Poliovirus (VDPV): Rare strains from mutated oral polio vaccine (OPV) Most common where immunization rates are low 6. Surveillance Systems Acute Flaccid Paralysis (AFP) Surveillance: Primary method for detecting new polio cases (especially in children under 15) Environmental Surveillance: Testing sewage and wastewater for poliovirus, often detects silent transmission Genetic Sequencing: Tracks virus evolution and transmission routes

11. 7. Eradication Milestones Year Milestone 1988 GPEI launched by WHO and partners 2000 Americas certified polio-free 2014 Southeast Asia region polio-free 2020 Africa declared wild polio-free 2023+ Ongoing outbreaks of cVDPV in select regions 8. Challenges to Eradication Vaccine misinformation and hesitancy Inaccessibility due to war, political unrest Logistical barriers in remote areas Emergence of cVDPV due to low OPV coverage

12. Clinical Manifestations of Polio Poliovirus infection can present in several distinct clinical forms, ranging from asymptomatic to life-threatening paralysis . The severity depends on the viral strain, host immunity, and extent of CNS involvement. 1. Inapparent (Subclinical) Infection – ~90–95% of cases No symptoms Individuals are still infectious and can spread the virus Only detectable through serological or virological testing 2. Abortive Poliomyelitis (Minor illness) – ~4–8% Mild, nonspecific symptoms No CNS involvement Symptoms: Low-grade fever Sore throat Malaise Headache Nausea and vomiting -- Diarrhea or constipation Lasts 2–5 days and resolves without sequelae

13. 3. Non-Paralytic Poliomyelitis – ~1–2% Involves aseptic meningitis (inflammation of meninges without bacterial infection) More severe symptoms and stiffness of neck, back, or legs Symptoms: Fever Headache Neck and back stiffness Muscle tenderness Photophobia Nausea and vomiting Usually resolves without paralysis, but discomfort can persist for days to weeks

14. 4. Paralytic Poliomyelitis – <1% The most severe form of the disease Virus invades the anterior horn cells of the spinal cord or the brainstem Types of Paralytic Polio: Spinal Polio: Most common Affects legs more than arms Leads to asymmetric flaccid paralysis Bulbar Polio: Affects cranial nerves , especially medulla oblongata Difficulty in breathing, swallowing, and speaking May lead to death if respiratory centers are involved Bulbospinal Polio: Combination of both spinal and bulbar involvement Can cause respiratory failure

15. 5. Post-Polio Syndrome (PPS) Affects 25–40% of polio survivors decades after recovery Progressive muscle weakness, fatigue , joint pain, and difficulty breathing Caused by gradual degeneration of motor neurons that compensated after acute infection Not caused by active virus replication

16. Diagnostic tools 1. Clinical Diagnosis Based on signs and symptoms , especially: Sudden onset of asymmetric flaccid paralysis No sensory loss Fever present at onset Case Definition for Surveillance (WHO): Any child <15 years with acute flaccid paralysis (AFP) Any person of any age with suspected poliomyelitis Note: Clinical symptoms alone are not definitive , and lab confirmation is essential. 2. Laboratory Diagnosis A. Stool Sample Analysis (Primary Test) Most reliable method Poliovirus is shed in feces Two stool samples collected 24–48 hours apart within 14 days of symptom onset Virus isolation via cell culture (e.g., L20B and RD cells) Followed by PCR testing and genetic sequencing to confirm virus type (wild, vaccine-derived)

17. B. Throat Swab Useful in early stages (virus present in oropharynx ) Less sensitive than stool sample Helps supplement stool testing C. Cerebrospinal Fluid (CSF) Analysis Used in suspected non-paralytic or paralytic polio Findings: Mild increase in white blood cells (WBCs) Slightly elevated protein levels No virus typically isolated from CSF Helps exclude bacterial meningitis or other causes D. Serology (Antibody Detection) Measures neutralizing antibodies against poliovirus serotypes Helpful in epidemiologic studies , not routine clinical diagnosis Rising antibody titers in paired serum samples may suggest recent infection

18. 3. Molecular Techniques A. Reverse Transcriptase Polymerase Chain Reaction (RT-PCR): Detects and differentiates poliovirus RNA in stool or throat specimens Rapid, sensitive, and allows genotyping (e.g., wild vs. vaccine-derived strain) B. Genetic Sequencing: Used to track virus origin , mutation, and transmission chain Crucial for outbreak investigation and surveillance 4. Imaging (for complications) MRI/CT Scans of the spinal cord and brain: May show inflammation in the anterior horn cells Used mainly in severe/paralytic cases. 5. Environmental Surveillance Testing of sewage or wastewater Detects silent transmission in communities Essential in countries with no clinical cases but high risk

19. Vaccine Development History of Polio 1. Pre-Vaccine Era Before vaccines, polio was one of the most feared diseases of the 20th century. Caused widespread epidemics, especially in the U.S. and Europe. Affected mainly children under age 5 , often leading to permanent paralysis or death . 2. Discovery of Poliovirus 1908 – Poliovirus identified by Karl Landsteiner and Erwin Popper . Researchers confirmed it was a viral disease transmitted via the fecal–oral route. 3. Development of Inactivated Polio Vaccine (IPV) – Jonas Salk Year: 1955 Type: Inactivated Polio Vaccine (IPV) – contains killed poliovirus of all 3 serotypes Method: Injection (intramuscular or subcutaneous) Trial: Massive field trial in 1954 involving over 1.8 million children in the U.S. Effectiveness: >90% effective in preventing paralytic polio

20. 4. Development of Oral Polio Vaccine (OPV) – Albert Sabin Year: 1961 (licensed in the U.S.) Type: Oral Polio Vaccine (OPV) – contains live, attenuated poliovirus Method: Oral drops, easy to administer Advantage: Induces intestinal immunity and helps interrupt community transmission. 5. Key Differences Between IPV and OPV Feature IPV (Salk) OPV (Sabin) Type Inactivated (killed) virus Live, attenuated virus Administration Injection Oral drops Immunity Type Systemic (bloodstream) Systemic + intestinal Risk of Reversion None Rare risk of vaccine-derived polio ( cVDPV ) Use Today Used in many countriesStill used in some global regions

21. 6. Global Eradication Efforts 1988: Global Polio Eradication Initiative (GPEI) launched by WHO, Rotary International, UNICEF, and CDC. OPV played a crucial role in reducing cases by >99% worldwide . Over 2.5 billion children vaccinated since then. 2016 onward: Many countries started transitioning to IPV-only schedules due to risks of cVDPV from OPV. 7. Recent Developments 2015: Type 2 wild poliovirus declared eradicated; trivalent OPV replaced with bivalent OPV (types 1 and 3) 2019: Type 3 wild poliovirus also declared eradicated 2021–Present: Introduction of novel OPV2 (nOPV2) to reduce risk of vaccine-derived outbreaks

22. Global Polio Eradication Initiatives 1. Why Global Eradication? Polio has no cure —only prevention through vaccination. It causes lifelong paralysis and can be fatal. Eradication saves millions of lives and billions of dollars in healthcare costs. Smallpox is the only other human disease successfully eradicated— polio is next in line . 2. Launch of the Global Polio Eradication Initiative (GPEI) Founded: 1988 Partners: World Health Organization (WHO) Rotary International U.S. Centers for Disease Control and Prevention (CDC) UNICEF Bill & Melinda Gates Foundation (joined later) Goal: Eradicate wild poliovirus (WPV) globally In 1988, polio paralyzed 350,000+ children per year in 125 countries .

23. 3. Key Strategies of GPEI Strategy Description Mass Immunization National Immunization Days (NIDs) using Oral Polio Vaccine (OPV) Surveillance of AFP Detecting Acute Flaccid Paralysis in children under 15 Environmental Surveillance Monitoring wastewater for poliovirus Targeted Mop-Up Campaigns Rapid response immunization in outbreak zones Switch from OPV to IPV Reduce risk of vaccine-derived poliovirus ( cVDPV ) Community Engagement Mobilizing local health workers, volunteers, and religious leaders 4. Major Milestones in Global Eradication Year Milestone 1988 GPEI launched 1994 Americas certified polio-free 2000 Western Pacific Region certified 2002 Europe declared polio-free 2014 Southeast Asia certified 2020 Africa certified wild polio-free 2024 Only 2 countries remain endemic : Pakistan and Afghanistan

24. 5. Successes 99% reduction in polio cases since 1988 Over 2.5 billion children vaccinated globally Millions of volunteers involved in outreach $17+ billion saved in future health costs 6. Remaining Challenges Endemic Regions: Pakistan & Afghanistan (due to conflict, misinformation, and inaccessibility) Vaccine-Derived Polio ( cVDPV ): Caused by weakened virus strains from OPV mutating in under-immunized areas Mistrust and Misinformation: Vaccine hesitancy due to political, cultural, or religious reasons Surveillance Gaps: Especially in conflict or remote zones

25. 7. New Tools and Innovations Novel OPV2 (nOPV2): Genetically engineered oral vaccine designed to reduce cVDPV risk Geographic Information Systems (GIS): Track vaccine coverage and plan outreach Mobile and cross-border vaccination teams: Reach nomadic and displaced populations. 8. Current Status (as of 2024) Country Status Pakistan Endemic (WPV1) Afghanistan Endemic (WPV1)Rest of WorldPolio -free(wild), occasional cVDPV outbreaks being contained

26. Challenges in Polio Eradication Even though polio has been eliminated in most of the world, several persistent challenges continue to delay its complete eradication. 1. Endemic Countries Polio remains endemic in only two countries : Afghanistan Pakistan Ongoing conflict, political instability , and inaccessibility hamper vaccination and surveillance efforts. Some areas remain off-limits to vaccinators due to security threats. 2. Vaccine-Derived Poliovirus ( cVDPV ) Cause: Live virus in Oral Polio Vaccine (OPV) mutates and spreads in under-immunized communities. cVDPV outbreaks have occurred in Africa, Asia, and the Middle East . Requires switching to Inactivated Polio Vaccine (IPV) or novel OPV2 (nOPV2) to reduce mutation risk.

27. 3. Vaccine Hesitancy and Misinformation Mistrust in vaccines fueled by: Religious or cultural beliefs Rumors of sterilization plots Social media-driven misinformation Misinformation leads to community resistance and refusal to vaccinate children. 4. Weak Health Systems Poor healthcare infrastructure in low-income or remote areas makes: Vaccine storage and delivery difficult (especially cold chain maintenance ) Training and mobilization of healthcare workers challenging Data collection and surveillance less accurate

28. 5.Population Movement Migration, displacement, and nomadic communities complicate: Tracking immunization status Sustaining high vaccination coverage Refugees or travelers can reintroduce poliovirus into polio-free areas. 6. Surveillance Gaps Inadequate Acute Flaccid Paralysis (AFP) and environmental surveillance lead to: Underreporting of cases Delayed outbreak response Surveillance is especially weak in conflict zones and remote rural areas .

29. 7. Funding Gaps Sustaining global eradication efforts requires billions of dollars annually . Declining interest as case numbers fall may lead to: Donor fatigue Delays in vaccine procurement and response activities 8. Operational Challenges Repeated campaigns in the same communities can cause: "Vaccine fatigue" among caregivers Burnout among frontline workers Logistical issues like transport, weather, and terrain affect vaccine delivery.

30. Case studies or recent data Here are several recent case studies highlighting key developments and data in polio epidemiology: 1. Pakistan – Wild Poliovirus Resurgence (2024–2025) Wild poliovirus (WPV1) detections in environmental samples spiked significantly—from 126 in 2023 to 402 in Pakistan in 2024 Cases reported : 74 in 2024 and 14 so far in 2025 (14 in Pakistan, 2 in Afghanistan) . New outbreak : First WPV1 case in 7 years recorded in Diamer , Gilgit-Baltistan , in June 2025—11th case since January Challenges : Vaccine refusals (60,000+ missed during April 2025 campaign), violence against vaccinators (police officer shot May 2025), and migrant movements exacerbating spread. Trigger factors : COVID-19 disruptions, flooding weakening sanitation, militant attacks, and misinformation.

31. 2. Papua New Guinea – Vaccine-Derived Poliovirus Outbreak (2025) Environmental detection : Poliovirus found in wastewater samples in Port Moresby and Lae Human cases : Two asymptomatic children tested positive for cVDPV2. Vaccination coverage : Only ~47–50% of children vaccinated; some districts as low as 8% Response measures : WHO, UNICEF, and Australian-led rapid immunization campaigns, environmental surveillance strengthening, community outreach via churches

32. 3. Gaza Strip – WPV Resurgence (2024) Epidemic declared : In July 2024 due to positive wastewater detections; first confirmed case August 16 in an infant Contributing factors : Overcrowding in shelters, damaged sanitation infrastructure, and movement post-ceasefire Campaign efforts : WHO resumed mass immunization in Feb 2025, reaching over 500,000 children (>95% coverage in initial rounds). Additional Highlights Madagascar : Outbreak of WPV1 variant (2020–2023) halted following emergency campaigns; declared over in May 2025 after no new cases for ≥12 months Global scope : As of June 2024, there were 74 ongoing cVDPV outbreaks across 39 countries, including 672 confirmed cases WHO Emergency Committee : Reported 62 WPV1 cases in 2024 (Pakistan & Afghanistan) and cited escalating environmental detections and increased geographic spread