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

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

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

Annually rotaviruses cause 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

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

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.

11 RNA segments

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.

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

VP1 VP1 is part of the inner core of the virus and one of three proteins comprising the innermost of three viral layers. It is the RNA-Dependent, RNA Polymerase for rotavirus. VP2 This protein is the main structural component of the innermost layer. VP3 The third part of the inner core of the virus, VP3 acts as the mRNA capping enzyme. VP4 Along with VP 7, VP4 makes up the outer capsid of virus. It is an 88 kDa protein that dimerizes to create 60 spikes on virus surface. VP4 is cleaved by the pancreatic enzyme trypsin to form VP 5 and VP 8. VP4 and its cleavage products are associated with cell attachment and invasion and cleavage is necessary for infectivity. VP4 is antigenic and induces neutralizing antibodies. The specific structure of this protein is used to determine the rotavirus P serotype, as well as host specificity, virulence and protective immunity.

VP5 VP6 VP7 VP8 NS1-6 NS4 acts as an enterotoxin and causes diarrhea VP5 is cleaved from the outer capsid protein VP4 in the presence of trypsin. It remains bound to virion post cleavage, and can be bound by neutralizing antibodies made to VP4. It is membrane associated and functions to permeablize host cell membranes to facilitate cell invasion. VP6 VP6 is a structural component that comprises the middle capsid. The specificity of this protein is used to determine the A-G groupings, and I, II sub-groupings of rotavirus. VP7 This 37 kD glycoprtein makes up the smooth portion of the outer capsid. It can induce neutralizing antibodies and determines the G serotype. It is also a highly variable portion of the virus capable of reassortment and possible crossover with animal strains of the virus. VP8 VP8 is the second cleavage product of VP4; binds sialic acid and acts the virus hemagglutinin NS1-6 NS4 acts as an enterotoxin and causes diarrhea

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

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

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

“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

Characteristics of Noroviruses Viruses are small, capsid viruses distinguishable by capsid morphology. Viruses are resistant to environmental pressure: detergents, drying, and acid. Viruses are transmitted by fecal-oral route in contaminated water and food. Viruses cause outbreaks of gastroenteritis. Disease resolves after 48 hours, without serious consequences Body_ID: B057003

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

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?

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

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 23

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

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

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

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

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

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