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Viral and Parasitic Gastroenteritis

Viral and Parasitic Gastroenteritis. Viral Gastroenteritis. Inflammation of the stomach and intestines caused by viruses, which is also known as the stomach flu This highly contagious illness spreads through close contact with people who are infected contaminated food or water

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Viral and Parasitic Gastroenteritis

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  1. Viral and Parasitic Gastroenteritis

  2. Viral Gastroenteritis • Inflammation of the stomach and intestines caused by viruses, which is also known as the stomach flu • This highly contagious illness spreads through • close contact with people who are infected • contaminated food or water • It can easily spread in close quarters • childcare facilities • Schools • nursing homes • cruise ships

  3. Viruses are responsible for up to ¾ of all infective diarrhoeas • Viral gastroenteritis is the second most common viral illness after upper respiratory tract infection • In developing countries, viral gastroenteritis is a major killer of infants who are undernourished • Rotaviruses are responsible for half a million deaths a year

  4. HEPATITIS • Hepatitis is inflammation of the liver • The disease can be caused by infections from parasites, bacteria, or viruses • Liver damage can also result from alcohol, drugs, or poisonous mushrooms • Hepatitis A, B, and C are clinically the most important forms of viral liver disease

  5. Persons at risk of hepatitis B infection include • 1) individuals with multiple sex partners • 2) men who have sex with men • 3) sex contacts of infected persons • 4) injection drug users • 5) household contacts of chronically infected persons • Death from chronic hepatitis B occurs in 15 to 25 percent of chronically infected persons

  6. Most hepatitis C infections result from illegal injection drug use • Transfusion-associated cases occurred prior to blood donor screening • now the incidence is less than 1 per 2 million transfused blood units • Fifty percent of those with hepatitis C go on to have • chronic liver disease • liver failure (cirrhosis) • liver cancer • Hepatitis C is the number one reason for receiving a liver transplant in the United States

  7. Classification of hepatitis viruses based on mode of transmission Classification of major viral agents causing hepatitis

  8. Hepatitis A Virus: Structure and Classification • Virus classification • Group: Group IV ((+)ssRNA) • Family: Picornaviridae • Genus: Hepatovirus • Species: Hepatitis A virus • Separate genus because ofdifferences with other enteroviruses • Naked icosahedral capsid • SS RNA (740 nucleotides) • Single serotype worldwide • Humans only reservoir Electron micrograph of hepatitis A virions

  9. Hepatitis A Virus Transmission • Fecal-oral • Close personal contact • e.g., household contact, sex contact, child day care centers • Contaminated food, water • e.g., infected food handlers • Blood exposure • rare

  10. Estimated prevalence of hepatitis A virus

  11. Hepatitis A: Pathogenesis • Incubation 4 weeks (range 2-6 weeks) • Oral cavity GI tract liver via blood • Replicates in hepatocytes (little damage to cells) released via bile to intestines 7-10 days prior to clinical symptoms • Liver damage and clinical syndrome result of immune response and not direct effect of virus

  12. Hepatitis A: Clinical Features • An acute illness with • discrete onset of symptoms • e.g. fatigue, abdominal pain, loss of appetite, nausea, vomiting • Jaundice • elevated serum aminotransferase levels, dark urine, light stool • Adults are usually more symptomatic • Patients are infective while they are shedding the virus in the stool- usually before the onset of symptoms • Most cases resolve spontaneously in 2-4 weeks • Complete recovery 99%

  13. Hepatitis A - Diagnosis • Detection of IgM antibody • IgG positive 1-3 weeks later; suggests prior infection or vaccination

  14. Hepatitis A - Treatment • Supportive: no specific role of antiviral therapy • Lifelong immunity likely after infection or vaccination

  15. PREVENTING HEPATITIS A • Hygiene • e.g., hand washing • Sanitation • e.g., clean water sources • Hepatitis A vaccine • pre-exposure

  16. HEPATITIS A VACCINES • Inactivated vaccine • Highly immunogenic • 97%-100% of children, adolescents, and adults have protective levels of antibody within 1 month of receiving first dose • essentially 100% have protective levels after second dose • Highly efficacious • In published studies, 94%-100% of children protected against clinical hepatitis A after equivalent of one dose

  17. HEPATITIS A VACCINES • 1st dose at time 0 • 2nd dose 6-12 months afterwards

  18. POST-VACCINATION TESTING • Not recommended • High response rate among vaccinees • Commercially available assay not sensitive enough to detect lower (protective) levels of vaccine-induced antibody

  19. DURATION OF PROTECTION AFTER VACCINATION • Protection begins 4 weeks after vaccine • Persistence of antibody • At least 5-8 years among adults and children • Efficacy • No cases in vaccinated children at 5-6 years • Mathematical models of antibody decline suggest protective antibody levels persist for at least 20 years • Other mechanisms, such as cellular memory, may contribute

  20. Hepatitis A Vaccine • Pre-exposure Vaccination • Persons at increased risk for infection • travelers to intermediate and high HAV-endemic countries • MSM (Men who have sex with men) • Drug users • Persons who have clotting factor disorders • persons with chronic liver disease • Communities with historically high rates of hepatitis A -routine childhood vaccination

  21. Hepatitis A Vaccine Immunogenicity, Side Effects • Immunogenicity in children, adolescents, adults • 94-100% positive 1 month after dose 1 • 99-100% positive after dose 2 • Most common side effects • Sore injection site (50%), headache (15%), malaise (7%) • No severe reactions known • Safety in pregnancy unknown (risk likely is low) • Currently licensed for aged 1 year and older

  22. Hepatitis B

  23. Hepatitis B: Structure • Member of the hepadnavirus group • Virionalso referred to as Dane particle • 42nm enveloped virus • Core antigens located in the center (nucleocapsid)

  24. Structure and Replication • Circular partially double stranded DNA of virus • Initial replication to complete circular DNA with subsequent transcription to make several mRNAs some of which are translated into viral proteins • One of the mRNAs is replicated with a reverse transcriptase making the DNA that will eventually be the core of the progeny virion • Some DNA integrates into host genome causing carrier state • Virus stable and resist many stresses making them more infectious

  25. Hepatitis B Virus TEM micrograph showing hepatitis B viruses The structure of hepatitis B virus

  26. Prevalence of chronic infection with hepatitis B virus, 2006

  27. Global Patterns of Chronic HBV Infection • High (>8%): 45% of global population • lifetime risk of infection >60% • early childhood infections common • Intermediate (2%-7%): 43% of global population • lifetime risk of infection 20%-60% • infections occur in all age groups • Low (<2%): 12% of global population • lifetime risk of infection <20% • most infections occur in adult risk groups

  28. Possible Outcomes of HBV Infection Acute hepatitis B infection 95% of infant-acquired infections 3-5% of adult-acquired infections Chronic HBV infection Chronic hepatitis 12-25% in 5 years Cirrhosis 20-23% in 5 years 6-15% in 5 years Hepatocellular carcinoma Liver failure Liver transplant Death Death

  29. 100 100 80 80 60 60 Chronic Infection 40 40 20 20 Symptomatic Infection 0 0 Birth 1-4 yrs 1-6 mos 7-12 mos Older Children and Adults Outcome of Hepatitis B Virus Infection by Age at Infection Chronic Infection (%) Symptomatic Infection (%)

  30. HBV Modes of Transmission • Sexual • Parenteral • Perinatal

  31. Low/Not High Moderate Detectable blood semen urine serum vaginal fluid feces wound exudates saliva sweat tears breast milk Concentration of HBV in Various Body Fluids

  32. Hepatitis B Symptoms • About 50%-60% of adults with HBV infection have no signs or symptoms • Those who do have symptoms might experience: • Jaundice • Fatigue • Abdominal pain • Loss of appetite • Nausea, vomiting • Joint pain

  33. HBV Pathogenesis • Virus enters hepatocytes via blood • Immune response (cytotoxic T cell) to viral antigens expressed on hepatocyte cell surface responsible for clinical syndrome • 5 % become chronic carriers (HBsAg> 6 months) • Higher rate of hepatocellular in chronic carriers, especially those who are “e” antigen positive • Hepatitis B surface antibody likely confers lifelong immunity • Hepatitis B Ab indicates low transmissibility

  34. Elimination of HBV Transmission • Prevent perinatal HBV transmission • Routine vaccination of all infants • Vaccination of children in high-risk groups • Vaccination of adolescents • all children up through age 18 • Vaccination of adults in high-risk groups

  35. Hepatitis B Vaccine • Licensed in 1982 • 3 dose series, typical schedule 0, 1-2, 4-6 months • 2 dose series (adult dose) • Protection ~30-50% dose 1; 75% - 2; 96% - 3 • lower in older, immunosuppressive illnesses • e.g., HIV, chronic liver diseases, diabetes, obese, smokers

  36. Hepatitis B Vaccine Safety • Side effects rare • Anaphylaxis estimated to occur in 1/600,000 doses given • No scientific data to link hepatitis B vaccine with multiple sclerosis (MS), other autoimmune diseases, autism

  37. Hepatitis B Vaccination • Routine infant • Ages 11-15 and through age 18 • Over 18 – high risk • Occupational risk • Hemodyalisis patients • All STD clinic clients • Multiple sex partners or prior STD • Inmates in Correctional settings • MSM • IDU • Institution for developmental disability

  38. Hepatitis C Virus

  39. Hepatitis C Structure and Classification • Member of the flavivirusfamily • Enveloped single stranded RNA virus • Humans and chimpanzees only known reservoirs • 6 serotypes (genotypes) and multiple subtypes • based on high variability of envelope glycoproteins

  40. Occupational Transmission of HCV • Inefficient by occupational exposures • Average incidence 1.8% following needle stick from HCV-positive source • Case reports of transmission from blood splash to eye • Prevalence 1-2% among health care workers

  41. Perinatal Transmission of HCV • Transmission only from women HCV-RNA positive at delivery • Average rate of infection 6% • Higher (17%) if woman co-infected with HIV • No association with • Delivery method • Breastfeeding • Infected infants do well • Severe hepatitis is rare

  42. Sexual Transmission of HCV • Occurs, but efficiency is low • Rare between long-term steady partners • Factors that facilitate transmission between partners unknown • Accounts for 15-20% of acute and chronic infections in the United States Partner studies

  43. Household Transmission of HCV • Rare but not absent • Could occur through percutaneous/mucosal exposures to blood • Contaminated equipment used for home therapies • Through sharing of contaminated personal material (razors, toothbrushes)

  44. Other Potential Exposures to Blood • No or insufficient data showing increased risk • intranasal cocaine use, tattooing, body piercing, acupuncture, military service

  45. Hepatitis C: Clinical Features • Acute infection asymptomatic in over 80% of patients, when present, acute illness usually mild • Acute symptoms include jaundice, nausea, abdominal pain, loss of appetite, dark urine

  46. Chronic Hepatitis C Factors Promoting Progression or Severity • Increased alcohol intake • Age > 40 years at time of infection • HIV co-infection • Other • Male gender • Chronic HBV co-infection

  47. Hepatitis C: Diagnosis • ELISA • usually positive within 2-5 months after infection • PCR • positive 1-2 weeks post infection

  48. Hepatitis D • Defective virus that requires co-infection with hepatitis B for replication • Enveloped with SS RNA genome • Only antigen encoded in the delta antigen

  49. Hepatitis D Virus Modes of Transmission • Percutaneous exposures • injecting drug use • Permucosalexposures • sex contact

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