Rotavirus

1. Rotavirus • Rota – means wheel-like in greek • Double-stranded, segmented RNA virus

2. Rotaviruses • 80 nm in diameter. • Also found in other mammals and birds, causing diarrhoea. • Account for 50-80% of all cases of viral gastroenteritis. • Usually endemic, but responsible for occasional outbreaks. • Causes disease in all age groups but most severe symptoms in neonates and young children. • Asymptomatic infections common in adults and older children. Symptomatic infections again common in people over 60. • Up to 30% mortality rate in malnourished children

3. 80% of the population have antibody against rotavirus by the age of 3. • More frequent during the winter. • 24-48 hr incubation period followed by an abrupt onset of vomiting and diarrhoea, a low grade fever may be present. • Diagnosed by electron microscopy or by the detection of rotavirus antigens in faeces by ELISA or other assays. • Live attenuated vaccines now available for use in children

4. Globally, it is estimated that 1.4 billion episodes of diarrhea occur in children less than five years of age annually • Annually rotaviruses cause • 5% of all deaths in children • 527,000 deaths • 80% of deaths are in infancy • > 100,000 in India • 39% of childhood hospitalisations for diarrhea

5. Rotaviruses are transmitted by the fecal-oral route. • Only 10 to 100 infectious virus particles are needed to cause infection. This amount can readily be acquired through contact with contaminated hands and objects. • Large numbers of viruses are shed in fecal matter, from 100 to 1000 particles per milliliter. • Hand-washing and sanitation does not work due to the resistant nature of the virus. Similar hospitalisation rates in countries with high and poor sanitation

6. The most effective antiseptics against rotavirus are alcohols, which have been found to reduce the number of viruses on the hands by greater than 99%. • Tap water alone, or tap water with regular soap reduces the titer by only 72-84%. ! Handwashing can reduce the spread of the virus, but is an ineffective means of eliminating it.

9. 11 RNA segments

10. Rotaviruses are usually categorized into seven groups A-G, with subgroups I and II based on the VP6 protein. • Rotavirus is further categorized into G and P serotypes. • The G serotype is specified by the glycoprotein VP7 of the outer capsid, which is coded by viral genes 7, 8, and 9. • The P serotype is specified by protein VP4, also on the outer capsid. It is a protease cleaved protein coded by gene 4 oft he virus genome.

11. VERY resistant to destruction • VP4 antigen: P serotype; 11 human rotaviruses • VP7 antigen: G serotype; 10 human rotaviruses • Commonly found strains:P[8]G1; P[8]G3; P[8]G4; and P[4]G2

15. Norovirus, Sapovirus • Family Caliciviridae • Non-enveloped RNA viruses • with ss [+] sense RNA • 27-35 nm in size • Contains single capsid protein

16. Norovirus, Sapovirus • Family Caliciviridae • Non-enveloped RNA viruses • with ss [+] sense RNA • 27-35 nm in size • Contains single capsid protein

17. Norwalk virus and “Norwalk-like”- Norovirus • “Sapporo-like” viruses - Sapovirus • Vesivirus • Lagovirus

18. “winter vomiting disease” 1968, Norwalk OH • Cause 40% of nonbacterial epidemics • 45% foodborne, 52% shell fish associated outbreaks • Explosive epidemics • camps, cruise ships, nursing homes • Food borne illness • raw shellfish

20. Survive on surfaces for several days • Survive in water chlorinated at routine levels (up to 10 ppm) • Survive freezing, heating up to 60°C • Evidently survive in steamed shellfish

21. Asymptomatic infections- seroconversion but • asymptomatic shedding of virus • Low infective dose (~10 pfu) • Viral excretion during convalesence (~ 2 wk.) • Protective immunity short-lived • NLV cross protection? • Blood group antigens predilection?

22. Diagnosis • Specimen- stool, vomitus, food, environmental swabs (during outbreak investigations) • RT-PCR • Serology for epidemiologic purposes • Immune EM is less used

23. EPIDEMIOLOGY : Outbreaks Cruise ships, schools, nursing homes, Can involve infants and school-age children Source usually is contaminated food and water (E.g. seafood-oyster and shellfish, salads, cake icing, raw fruit etc.) Rapid secondary spread

25. CDC recommends environmental disinfection of non-porous surfaces with 1000 ppm bleach solution (1 part bleach: 50 parts water)

26. HUMAN ASTROVIRUS Genus Astrovirus Family Astroviridae Human serotypes: HuAstV 1-8

27. Small ss RNA virus • Non-enveloped • 27-32nm in size • Round with an unbroken, smooth surface • EM appearance of a 5 or 6 pointed star within smooth edge • Contain 3 structural proteins • Genome has been sequenced

28. Infants and children are most often affected • Elderly and immune compromised persons also • Short incubation period 1-4 days • Nausea, vomiting, abdominal cramping and watery diarrhea • Constitutional symptoms-fever, malaise, headache

29. Endemic worldwide • True disease burden is not yet clear • Mainly in children <7 years of age • Transmission- person-to-person [fecal-oral] • Outbreaks due to fecal contamination of sea-food or water

30. EM (virus shed in stool in great numbers) • EIA • RT-PCR