II MBBS students-CBME batch-Microbiology Subject

1. VIRUSES CAUSING DIARRHEA
MI 3.1
Dr V S Vatkar
Associate Professor
Department of Microbiology
D Y Patil Medical College, Kolhapur

2. VIRUSES RESPONSIBLE FOR DIARRHEA
 Rotavirus
 Caliciviruses: Norovirus, Sapovirus
 Astrovirus
 Adenovirus
 Respiratory viruses
 Nipah virus

3. ROTAVIRUS
 Most common cause of
diarrhea in children
 Morphology: family
Reoviredae
 60-80 nm
 ds RNA: 11 segments
 Six structural viral
proteins (VP1 VP7,
Except VP5)
 VP6: group significant
 VP7: forms outer capsid
layer
 VP4: forms spike

4. STRUCTURE OF ROTAVIRUS

5. CLASSIFICATION OF ROTAVIRUS
 Traditional groups:
 Classified into major 7 groups (A-G)
 Based on antigenic variation of group specific VP6
 Most of the human diarrhea : caused by group A
 Binary system of typing: recent classification
 Genotyping method(gene coding for VP4 Ag)
 Serotyping method: based on VP7 Ag
 Currently 19G & 28(P), G 1 P(8) type common in
India, areas with poor hygiene.

6. PATHOGENESIS
 Transmitted by fecal-oral route
 Destroy enterocytes of small intestine &
spread to gastric & colonic mucosa.
 Multiply in the cytoplasm of enterocytes &
destroy their transport mechanism resulting
in secretory diarrhea
 Non structural protein NSP4 acts as
enterotoxin induces secretion by epithelial
cells.

7. CLINICAL FEATURES
 IP: 1-3 days
 Abrupt onset
 Vomiting followed by watery diarrhea, fever,
abdominal pain
 Recovery usually occurs, few children may suffer
from loss of electrolytes & fluids leading to
dehydration
 Infection in adults is usually asymptomatic (Group B
rotavirus outbreaks of sever gastroenteritis in adults
in China)

8. EPIDEMIOLOGY
 Severe infantile gastroenteritis
 Most important/ commonest cause of acute
gastroenteritis in young children
 World wide, about 3-4 billon diarrheal episodes in
children occur annually , nearly 1 million deaths
especially from sub-Saharan Africa & Southern Asia
 In Developing countries like India: seen in younger
age, less seasonal,
 Temperate climate: Group A outbreaks in cooler
months

9. LABORATORY DIAGNOSIS
 Direct detection of virus : feces collected in early
illness, virus detection can be done by
 Immunoelectron microscopy (IEM)
 Isolation of virus is difficult
 Detection of viral Ag: detected by stool ELISA &
latex agglutination test
 RT-PCR most sensitive detection method from stool
 Typing method: G serotype & P serotype :
detected by RNA sequence typing & neutralization
test
 ELISA: detects raised Ab titer, useful for sero-
prevalence purpose.

10. TREATMENT & PROPHYLAXIS
 Mainly supportive treatment to correct loss of water &
electrolytes (ORS or I/V fluids)
 Prevention:
 Vaccine: two brands : available
 Rotavac: live attenuated Rotavirus strain 116E
(G9P[10] strain)
 Manufactured by Bharat Biotech
 Three doses (5 drops/dose), given orally at 6,10, 14
weeks along with DPT & OPV
 Efficacy : 55%
 S/E: irritable, fever, crying, diarrhea (no vaccine induced
intussusception)

11.  Rotarix:
 Live attenuated G1P[8] strain
 Provides cross protection against G3, G4 & G9
 Has to be reconstituted before use
 Two doses : 1st t 6 week & 2nd :given after 4weeks
 General prevention:
 To improve hygiene, sanitation in the community
 Strict hand hygiene to prevent transmission from
infected person

12. OTHER VIRUSES CAUSING GASTROENTERITIS
(DIARRHEA)
 Family Caliciviridae:
 a) genus Norovirus includes Norwalk virus b)
genus Sapovirus includes sapporo like viruses.
 NORWALK viruse: important cause of epidemic
viral acute gastroenteritis in adults.
 Common in winter season in temperate climate
 C/F: IP- 12-48 hrs, diarrhea, abdominal pain,
nausea, vomiting
 Cause of infection: contaminated food like salad,
fruits, shellfish (oyster) or water, infected person

13.  Sapovirus : sporadic cases, occasional outbreaks
in infants, young children & adults
 Lab diagnosis & treatment : same as Rotavirus
 ADENOVIRUS: common cause of endemic
diarrheal illness (acute gastroenteritis) with keratitis
in infants & young adults.
 ASTROVIRUSES: Star like morphology seen under
electron microscope. Positive sense RNA, causes
sporadic cases & occasionally diarrheal outbreaks
in infants, young children & elderly, rarely causes
acute gastroenteritis.

14.  Respiratory Viruses:
 SARS, Corona virus
 Influenza A/ H1N1
 H5N1
 Torovirus/ Picobirnaviruses: causes diarrheal
infection in animals
 Their role as primary cause of gastroenteritis in
human is unclear.
 Nipah virus: reservoirs : fruit bats. Rarely causes
diarrhea