RotavirusRotavirus Rota – means wheel-like in greekRota – means wheel-like in greek Double-strandedDouble-stranded, segmented , segmented RNA RNA

virusvirus

RotavirusesRotaviruses

80 nm in diameter.80 nm in diameter. Also found in other mammals and birds, causing diarrhoea.Also found in other mammals and birds, causing diarrhoea. Account for 50-80% of all cases of viral gastroenteritis.Account for 50-80% of all cases of viral gastroenteritis. Usually endemic, but responsible for occasional outbreaks.Usually endemic, but responsible for occasional outbreaks. Causes disease in all age groups but most severe symptoms in Causes disease in all age groups but most severe symptoms in

neonates and young children. neonates and young children. Asymptomatic infections common in adults and older children. Asymptomatic infections common in adults and older children.

Symptomatic infections again common in people over 60.Symptomatic infections again common in people over 60. Up to 30% mortality rate in malnourished childrenUp to 30% mortality rate in malnourished children

80% of the population have antibody against rotavirus by 80% of the population have antibody against rotavirus by the age of 3. the age of 3.

More frequent during the winter.More frequent during the winter.

24-48 hr incubation period followed by an abrupt onset 24-48 hr incubation period followed by an abrupt onset of vomiting and diarrhoea, a low grade fever may be of vomiting and diarrhoea, a low grade fever may be present.present.

Diagnosed by electron microscopy or by the detection of Diagnosed by electron microscopy or by the detection of rotavirus antigens in faeces by ELISA or other assays.rotavirus antigens in faeces by ELISA or other assays.

Live attenuated vaccines now available for use in childrenLive attenuated vaccines now available for use in children

Globally, it is estimated that 1.4 billion Globally, it is estimated that 1.4 billion episodes of diarrhea occur in children episodes of diarrhea occur in children

less than five years of age annuallyless than five years of age annually

Annually rotaviruses cause Annually rotaviruses cause – 5% of all deaths in children5% of all deaths in children– 527,000 deaths527,000 deaths

80% of deaths are in infancy 80% of deaths are in infancy > 100,000 in India> 100,000 in India

– 39% of childhood hospitalisations for 39% of childhood hospitalisations for diarrheadiarrhea

Rotaviruses are transmitted by the fecal-oral Rotaviruses are transmitted by the fecal-oral route. route.

Only 10 to 100 infectious virus particles are Only 10 to 100 infectious virus particles are needed to cause infection. This amount can needed to cause infection. This amount can readily be acquired through contact with readily be acquired through contact with contaminated hands and objects.contaminated hands and objects.

Large numbers of viruses are shed in fecal Large numbers of viruses are shed in fecal matter, from 100 to 1000 particles per milliliter.matter, from 100 to 1000 particles per milliliter.

Hand-washing and sanitation does not work due Hand-washing and sanitation does not work due to the resistant nature of the virus.to the resistant nature of the virus. Similar Similar hospitalisation rates in countries with high and hospitalisation rates in countries with high and poor sanitationpoor sanitation

The most effective antiseptics against rotavirus The most effective antiseptics against rotavirus are alcohols, which have been found to reduce are alcohols, which have been found to reduce the number of viruses on the hands by greater the number of viruses on the hands by greater than 99%.than 99%.

Tap water alone, or tap water with regular soap Tap water alone, or tap water with regular soap

reduces the titer by only 72-84%. reduces the titer by only 72-84%. !! Handwashing can reduce the spread of the Handwashing can reduce the spread of the virus, but is an ineffective means of eliminating virus, but is an ineffective means of eliminating it. it.

11 RNA segments11 RNA segments

Rotaviruses are usually categorized into seven groups Rotaviruses are usually categorized into seven groups

A-G, with subgroups I and II based on the VP6 protein.A-G, with subgroups I and II based on the VP6 protein.

Rotavirus is further categorized into G and P Rotavirus is further categorized into G and P serotypes. serotypes.

The G serotype is specified by the glycoprotein VP7 of The G serotype is specified by the glycoprotein VP7 of the outer capsid, which is coded by viral genes 7, 8, the outer capsid, which is coded by viral genes 7, 8, and 9. and 9.

The P serotype is specified by protein VP4, also on the The P serotype is specified by protein VP4, also on the outer capsid. It is a protease cleaved protein coded by outer capsid. It is a protease cleaved protein coded by

gene 4 oft he virus genome.gene 4 oft he virus genome.

VERY resistant to VERY resistant to destructiondestruction

VP4 antigen: P VP4 antigen: P serotype; serotype; 11 human 11 human rotaviruses rotaviruses

VP7 antigen: G VP7 antigen: G serotype; serotype; 10 human 10 human rotavirusesrotaviruses

Commonly found Commonly found strains:strains:P[8]G1; P[8]G3; P[8]G1; P[8]G3; P[8]G4; P[8]G4; and P[4]G2and P[4]G2

VP1VP1

VP1 is part of the inner core of the virus and one of three VP1 is part of the inner core of the virus and one of three proteins comprising the innermost of three viral layers. It proteins comprising the innermost of three viral layers. It is the RNA-Dependent, RNA Polymerase for rotavirus.is the RNA-Dependent, RNA Polymerase for rotavirus.

VP2VP2 This protein is the main structural component of the This protein is the main structural component of the

innermost layer.innermost layer.

VP3VP3 The third part of the inner core of the virus, VP3 acts as The third part of the inner core of the virus, VP3 acts as

the mRNA capping enzyme.the mRNA capping enzyme.

VP4VP4 Along with VP 7, VP4 makes up the outer capsid of virus. Along with VP 7, VP4 makes up the outer capsid of virus. It is an 88 kDa protein that dimerizes to create 60 spikes It is an 88 kDa protein that dimerizes to create 60 spikes on virus surface. VP4 is cleaved by the pancreatic on virus surface. VP4 is cleaved by the pancreatic enzyme trypsin to form VP 5 and VP 8. VP4 and its enzyme trypsin to form VP 5 and VP 8. VP4 and its cleavage products are associated with cell attachment cleavage products are associated with cell attachment and invasion and cleavage is necessary for infectivity. and invasion and cleavage is necessary for infectivity. VP4 is antigenic and induces neutralizing antibodies. The VP4 is antigenic and induces neutralizing antibodies. The specific structure of this protein is used to determine the specific structure of this protein is used to determine the rotavirus P serotype, as well as host specificity, virulence rotavirus P serotype, as well as host specificity, virulence and protective immunityand protective immunity..

VP5VP5 VP5 is cleaved from the outer capsid protein VP4 in the VP5 is cleaved from the outer capsid protein VP4 in the presence of trypsin. It remains bound to virion post presence of trypsin. It remains bound to virion post cleavage, and can be bound by neutralizing antibodies cleavage, and can be bound by neutralizing antibodies made to VP4. It is membrane associated and functions to made to VP4. It is membrane associated and functions to permeablize host cell membranes to facilitate cell permeablize host cell membranes to facilitate cell

invasion.invasion.

VP6VP6 VP6 is a structural component that comprises the middle VP6 is a structural component that comprises the middle capsid. capsid. The specificity of this protein is used to The specificity of this protein is used to determine the A-G groupings, and I, II sub-groupings of determine the A-G groupings, and I, II sub-groupings of rotavirus.rotavirus.

VP7VP7 This 37 kD glycoprtein makes up the smooth portion of This 37 kD glycoprtein makes up the smooth portion of the outer capsid. the outer capsid. It can induce neutralizing antibodies It can induce neutralizing antibodies and determines the G serotype.and determines the G serotype. It is also a highly It is also a highly variable portion of the virus capable of reassortment variable portion of the virus capable of reassortment and possible crossover with animal strains of the virus.and possible crossover with animal strains of the virus.

VP8VP8 VP8 is the second cleavage product of VP4;VP8 is the second cleavage product of VP4; binds sialic binds sialic

acid and acts the virus hemagglutininacid and acts the virus hemagglutinin

NS1-6NS1-6

NS4NS4 acts as an acts as an enterotoxinenterotoxin and causes diarrhea and causes diarrhea

Norovirus, SapovirusNorovirus, Sapovirus

•Family Family CaliciviridaeCaliciviridae

•Non-enveloped RNA virusesNon-enveloped RNA viruses

– with ss with ss [+] sense[+] sense RNA RNA

•27-35 nm in size27-35 nm in size

•Contains single capsid Contains single capsid

proteinprotein

Norovirus, SapovirusNorovirus, Sapovirus

•Family Family CaliciviridaeCaliciviridae

•Non-enveloped RNA virusesNon-enveloped RNA viruses

– with ss with ss [+] sense[+] sense RNA RNA

•27-35 nm in size27-35 nm in size

•Contains single capsid Contains single capsid

protein protein

Norwalk virus and “Norwalk-like”Norwalk virus and “Norwalk-like”- - NorovirusNorovirus

““Sapporo-like” virusesSapporo-like” viruses - Sapovirus - Sapovirus VesivirusVesivirus LagovirusLagovirus

““winter vomiting disease” 1968, winter vomiting disease” 1968, Norwalk OHNorwalk OH

Cause 40% of nonbacterial epidemicsCause 40% of nonbacterial epidemics– 45% foodborne, 52% shell fish 45% foodborne, 52% shell fish

associated outbreaksassociated outbreaks Explosive epidemicsExplosive epidemics

– camps, cruise ships, nursing homescamps, cruise ships, nursing homes Food borne illnessFood borne illness

– raw shellfishraw shellfish

Characteristics of NorovirusesCharacteristics of Noroviruses

Body_ID: Body_ID: B057003B057003

Viruses are small, capsid viruses distinguishable by Viruses are small, capsid viruses distinguishable by capsid morphology.capsid morphology. Viruses are resistant to environmental pressure: Viruses are resistant to environmental pressure: detergents, drying, and acid. detergents, drying, and acid.

Viruses are transmitted by fecal-oral route in Viruses are transmitted by fecal-oral route in contaminated water and food. contaminated water and food.

Viruses cause outbreaks of gastroenteritis. Viruses cause outbreaks of gastroenteritis.

Disease resolves after 48 hours, without serious Disease resolves after 48 hours, without serious consequencesconsequences

Survive on surfaces for several daysSurvive on surfaces for several days Survive in water chlorinated at routine Survive in water chlorinated at routine

levels (up to 10 ppm)levels (up to 10 ppm) Survive freezing, heating up to 60°CSurvive freezing, heating up to 60°C Evidently survive in steamed shellfishEvidently survive in steamed shellfish

Asymptomatic infections- Asymptomatic infections- seroconversion butseroconversion but

asymptomatic shedding of virusasymptomatic shedding of virus Low infective dose (~10 pfu)Low infective dose (~10 pfu) Viral excretion during convalesence (~ Viral excretion during convalesence (~

2 wk.)2 wk.) Protective immunity short-livedProtective immunity short-lived NLV cross protection?NLV cross protection? Blood group antigens predilection?Blood group antigens predilection?

DiagnosisDiagnosis

Specimen- stool, vomitus, food, Specimen- stool, vomitus, food,

environmental swabs (during outbreak environmental swabs (during outbreak

investigations)investigations)

RT-PCRRT-PCR

Serology for epidemiologic purposesSerology for epidemiologic purposes

Immune EM is less usedImmune EM is less used

EPIDEMIOLOGY : OutbreaksEPIDEMIOLOGY : Outbreaks

Cruise ships, schools, Cruise ships, schools, nursing homes, nursing homes,

Can involve infants and Can involve infants and school-age childrenschool-age children

Source usually is Source usually is contaminated food and contaminated food and water (E.g. seafood-water (E.g. seafood-oyster and shellfish, oyster and shellfish, salads, cake icing, raw salads, cake icing, raw fruit etc.) fruit etc.)

Rapid secondary spreadRapid secondary spread

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

HUMAN HUMAN ASTROVIRUSASTROVIRUS

Genus Astrovirus

Family Astroviridae

Human serotypes: HuAstV 1-8

Small ss RNA virus Small ss RNA virus Non-enveloped Non-enveloped 27-32nm in size27-32nm in size Round with an unbroken, smooth surfaceRound with an unbroken, smooth surface EM appearance of a 5 or 6 pointed star EM appearance of a 5 or 6 pointed star withinwithin

smooth edge smooth edge Contain 3 structural proteinsContain 3 structural proteins Genome has been sequencedGenome has been sequenced

Infants and children are most often Infants and children are most often affectedaffected

Elderly and immune compromised Elderly and immune compromised persons alsopersons also

Short incubation period 1-4 daysShort incubation period 1-4 days Nausea, vomiting, abdominal cramping Nausea, vomiting, abdominal cramping

and watery diarrheaand watery diarrhea Constitutional symptoms-fever, malaise, Constitutional symptoms-fever, malaise,

headacheheadache

Endemic worldwideEndemic worldwide

True disease burden is not yet clear True disease burden is not yet clear

Mainly in children <7 years of ageMainly in children <7 years of age

Transmission- person-to-person [fecal-Transmission- person-to-person [fecal-

oral]oral]

Outbreaks due to fecal contamination Outbreaks due to fecal contamination

of of

sea-food or watersea-food or water

EM (virus shed in stool in EM (virus shed in stool in

great numbers)great numbers)

EIA EIA

RT-PCRRT-PCR