VIRAL GASTROENTERITIS

VIRAL GASTROENTERITIS ROTAVIRUS Linear ds RNA, 11 segments, with 70 nm diameter ADENOVIRUS Linear ds DNA, with 80 – 110 nm diameter Types 40 and 41 CALICIVIRUS Linear positive sense ss RNA, with 35 nm diameter Norovirus causes diarrhea Hepatitis E virus causes hepatitis ASTROVIRUS Linear positive sense ss RNA, with 30 nm diameter

ROTAVIRUSES DISEASES Gastroenteritis (diarrhea), especially in young children

PROPERTIES Member of the Reovirus family (reo; respiratory enteric orphan) Non-enveloped, dsRNA viruses with icosahedral symmetry 11 segments RNA RNA-dependent RNA polymerase (human cells do not have an RNA polymerase that can synthesize mRNA from double-stranded RNA template) The capsid has double shell 6 serotypes (A-F)

TRANSMISSION Fecal-oral route Season: winter By age of 6 years, the majority of children have antibodies to at least one serotype.

PATHOGENESIS Rotavirus replicates in the mucosal cells of the small intestine, damaging the transport mechanisms with consequent loss of fluids and electrolytes. No inflammation occurs and the diarrhea is non-bloody.

CLINICAL FINDINGS Babies under 2 years are the main victims. Nausea, vomiting and watery, non-bloody diarrhea Dehydration is the main complication

LABORATORY DIAGNOSIS Detection of rotavirus in the stool by ELISA or RIA Latex agglutination Immunoelectron microscopy

ROTAVIRUSES

TREATMENT No antiviral drug is available. Rehydration Rotavirus vaccine (RotaShield) contains four serotypes of live, attenuated virus. In 1999, a hold was placed on the vaccine because of the risk of intussusception.

ADENOVIRUSES

ADENOVIRUSES Non-enveloped DNA virus with icosahedral capsid Adenovirus is the only virus with a fiber protruding from each of the 12 vertices of the capsid. The fiber is the organ of attachment and is a hemagglutinin. There are 41 known antigenic serotypes; the fiber protein is main type-specific antigen. Types 40 and 41 cause infantile gastroenteritis. Laboratory diagnosis: Adenovirus antigen detection in patient’s stool Isolation of the virus in cell culture Detection 4-fold or greater increase in antibody titre

ADENOVIRUSES

NOROVIRUS

NOROVIRUS Calicivirus Naked icosahedral capsid ssRNA, linear, non-segmented with positive polarity

NOROVIRUS Causes outbreaks of gastroenteritis in schools, camps and cruise ships. Previously named Norwalk virus for an outbreak in school in Norwalk, Ohio in 1969. Children tend to suffer from extensive vomiting, while adults are more likely to experience diarrhea. Infection susceptibility: People with blood group O has increased risk of infection People with blood group B has decreased risk of infection Transmission: fecal-oral, sewage-polluted water supply, shellfish taken from contaminated water. Diagnosis: detection of viral antigen in stool using ELISA.

ASTROVIRUS

ASTROVIRUS Linear, positive sense ssRNA virus The surface of the icosahedral capsid has five or six-pointed star appearance.

ASTROVIRUS Causes outbreaks of diarrhea in children under 5 years Mild gastroenteritis, fecal-oral transmission Diagnosis: detection of viral antigen