Mcim Lecture 11 Flashcards
0
Q
Gastrointestinal (enteric) viruses
- 70% of all cases of human gastroenteritis are due to viruses( rest are bacteria, parasitic infections)
- many different types of enteric viruses( but 4 types are responsible for the most cases of disease) what are they?
A
1) rotavirus: most common cause of diarrhea in kids under 5yr (can occur in adults, but with milder symptoms)
2) adenovirus: mainly kids under 2yr; occurs year round
3) astrovirus- all ages, mostly in winter months
4) calicivirsus( large group that inc. norivirus )- all ages, all the time
1
Q
Representative viral diseases(6)
A
- Skin( and beyond)
- herpes simplex virus
- human papilloma virus - Gastrointestinal viruses
- Viruses of the central nervous system
- “Blood-borne” viruses
- Respiratory viruses
- Emerging viral diseases (Ebola)
2
Q
Different types of enteric viruses all share some common features, what are they? (2)
A
- Mainly transmitted by fecal-oral route ex) contact with, and ingestion of, fecal material containing virus
- Similar disease progression: 1-3 days from 1st contact to symptoms ex. The “incubation period”
- similar symptoms (vomiting, diarrhea, nausea, abdominal pain)
- usually a self- limiting infection(3-4 days) in otherwise healthy humans
therefore- determining which virus is actually causing a GI disease can only be done by laboratory testing
3
Q
What is Norovirus? Aka. Norwalk virus
A
naked RNA virus; identified in 1972 after outbreak of GI disease in Norwalk, Ohio
- other viruses with similar features were later identified and called “Norwalk-like” therefore, general term is “Norovirus”
very stable in the environment- survives 10ppm chorine, freezing, heating to 60C
- fecal- contaminated food/water Is usual source of injection
- can’t tell by looking at/smelling food that it carries Norovirus
- low infectious dose- 10-100 virus able to cause disease
- long term close-quarter contact is a major risk factor ex) hospitals, nursing care homes, day cares, cruise ships etc
4
Q
How does Norovirus cause disease?
A
- ->viruses attach, enter, and replicate in intestinal epithelial cells
- ->lyric infection cycle destroys host cells
- new viruses released into feces: re transmission
- localized damage to gut epithelium: nausea, vomiting, abdom.pain, also: loss of absorptive capacity(diarrhea)
- recovery via immune response( but no long term immunity)
5
Q
Typical clinical features of Norovirus?
A
- 2-3 day incubation period prior to symptoms
- 1-5 days of watery diarrhea + nausea/vomiting/ abdominal pain
- severe dehydration is the main clinical concern: tachycardia, hypotension
- supportive therapy only ex) no effective anti vitals: fluid replacement to prevent dehydration
- can continue to shed virus for 2 weeks after symptoms disappear: most likely source of new infections
6
Q
Viruses of the CNS?
A
aka “neurotrophic” viruses( viruses able to infect nerve cells)
- ->encephalitis(inflammation of the brain)
- ->meningitis( inflammation of protective membrane covering brain)
- ->poliomyelitis ( destruction of motor neurone in brain, spine)
wide variety of viruses–>mumps, measles, rabies, herpes, enterviruses, Etc
Infection usually starts somewhere else Ex) poliovirus (fecal-oral transmission) -->enters intestinal epithelial cells -->enters intestinal lymphoid tissues -->absorbed into blood -->Crosses blood-brain barrier -->enters neurons
7
Q
West Nile virus (wnv)
A
- small enveloped RNA virus
- ex, of a “vector-borne” virus: a virus whose primarily(but not only) mode of transmission is via a living carrier( a vector)- usually an insect
- first seen in 1937 in west Nile region of Uganda and remained mostly localized to Africa, west Asia, Middle East: sporadic outbreaks over past 70 years
8
Q
West Nile cycle transmission cycle?
A
- natural host for WNV is birds(mainly crows, but others also)
- primary transmission cycle is from Bird to bird via culex tarsalis mosquito
- humans(and other animals) are “incidental” hosts
- -> acquire virus after bite from infected mosquito
- -> infected human now becomes a “dead-end” host- cannot re-transmit WNV to other humans via mosquito bite
- NO evidence of transmission through casual contact with birds and cannot be spread person to person via casual contact– but: other ways for direct human to human transmission: mother to child during birth, organ transplants, blood transfusion
9
Q
West Nile Virus clinical presentation
A
- 80% of WNV-infected people Have no symptoms
- 20% develop mild “west Nile fever”
- -> 3 to 4 days after bite
- -> fever headache, body ache, rash, swollen glands
- -> lasts 3 to 4 days, then recovery w/o long term effects
- 1% develop more severe encephalitis (usually pt. >50yr)
- viral replication in the brain leads to inflammation–> headache, high fever, neck stiffness, disorientation
- paralysis, seizures (leading to death in severe cases)
- symptoms subside over time, but neurological damage may be permanent
10
Q
West Nile clinical presentation
A
- no effective anti-viral therapy; no human vaccine
- immunity after natural infection is probable(short or long term??)
- best preventative measure is to avoid mosquito exposure
- Saskatchewan: 1st appeared in 2003: –> 947 confirmed cases: 10 without symptoms, 868 with west bile fever, 62 with encephalitis, 7 deaths
11
Q
“Blood borne” viruses
A
- viruses which infect various organs or cells, but whose presence can routinely be seen in the bloodstream (& other bodily fluids)–> transmitted by direct contact with blood/bodily fluids
- major BBVs: hep B, Hep C, HIV
- minor BBVs: hep A & D, West Nile virus, cytomegalovirus
- your biggest worry as a health care provider ex) hep B: 1 in 3 risk of infection when in direct contact with blood from an infected person(ex. Needle stick injury)
- hep c: 1 in 30
- HIV: 1 in 300
12
Q
Hep C virus
A
Hepatitis= inflammation of the liver
- -> jaundice, poor appetite & weight loss, fatigue, muscle & joint pain
- -> progressive loss of liver function over time, often requiring liver transplants to avoid death( = 40% of liver transplants are due to HCV)
- note: HCV is only one possible cause of “hepatitis”
- -> first described clinically in early 1970s ( non- A, non-B hep)
- -> identified as a unique virus in 1989
- Canada– 250, 000
13
Q
Hepatitis C virus
A
- enveloped RNA virus with a small ( 10 genes) genome
- very rapid replication rate–> up to 10^12 new viruses produced per day during an active infection
- 7 different “genotypes” (plus> 50 sub types) –> different in RNA sequence of “non- structural” genes
- note: the different HCV genotypes are differently thoughout the world (ex. North America- geno. 1: Middle East & Africa- geno 4; etc) and differ in how they respond to anti-viral therapy
14
Q
Transmission of HCV?
A
- blood-borne ex) via exchange of blood or body fluids):
- -> IV drug use with shared needles:65% of new cases
- -> blood transfusion, organ transplants: < 0.1% (vs 4% pre- 1990)
- -> occupational exposure to blood (ex. Health care workers): 3%
- -> hemodialysis: 1%
- other known routes( although relative risk is low or unknown):
- -> household exposure or unprotected sex with HCV partner
- -> mother- fetus transmission( occurs in= 5% of HCV mothers)
- -> body piercing, tattooing, etc with improperly sterilized equipment
- HIV is NOT transmitted by:
- coughing, sneezing, hugging, kissing & other casual contact
- sharing eating utensils or via food or water
- Mosquitos or other biting insects
