Summary - IPC Module 4 Flashcards
Blood-borne pathogens of greatest concern:
HBV (hepatitis B), HCV (hepatitis C) and HIV (AIDS)
Risk after stick with used needle / no gloves
HIV – 0.3%
HCV – 3.0%
HBV – 30.0%
(gloves reduce risk by 50% as blood wiped off outside of glove as needle passes through it)
Hepatitis Symptoms
inflammation of liver
symptoms: jaundice, dark urine, pale feces
causes: viruses
(Hep A, B, C, D, E), bacteria, parasites, alcohol, chemicals
Hepatitis A Summary
Previously called: infectious hepatitis (but all viral hepatitis infectious), short incubation hepatitis (but incubation varies for all types)
Causative agent: HAV; naked
Entry into host and replication: HAV-contaminated food or H20 → ingested by new host replicates in mouth, intestine, and liver → excreted via bile duct into intestinal tract → HAV in feces
HAV infection: most hosts get typical hepatitis symptoms usually no permanent liver damage; don’t usually die
Chronic carriers: no
Diagnosis: test blood for anti-HAV antibodies
Transmission: via food or H20 contaminated with feces or saliva
Prevention: keep stool and drool out of food hepatitis A vaccine for travelers going to areas of poor sanitation (pre-exposure protection) and for identified contacts of people with hepatitis A (post-exposure protection)
Hepatitis B Summary
Previously called: serum hepatitis (but found in other body fluids too) long incubation hepatitis (but incubation time variable)
Causative agent: HBV; enveloped
Entry into host and replication: HBV → blood or mucous membrane → replicates in liver → HBV in blood, semen, vaginal secretions, CSF, …
HBV infection: most hosts asymptomatic
some get typical hepatitis symptoms
a few get fulminant form: rapid, severe, can be fatal
Chronic carriers: yes; 5-10% (even if asymptomatic)
implications: serve as reservoir for HBV; body fluids
infectious for several years
great incidence of hepatic cancer down road
Transmission: usually via blood - most infectious source; minute amount will do it potentially infective activities: anything leading to blood-blood or blood-mucous membrane contact: sharing needles, needle jabs, blood spill on broken skin, tattooing, acupuncture, bloody sex, mom can transmit to fetus, other infective fluids: semen, vaginal secretions, CSF, breast milk, saliva - when: in acute phase and in chronic carrier phase, feces not infective, as with HAV
Diagnosis: test blood for serological markers
HBsAg used to initially diagnose HBV infection
(surface Ag)
anti-HBs presence indicates successful immunization
(surface Ab) or patient recovering from HBV
Infection
Potential risk situations at work:
anything where blood-blood or blood-mucous membrane contact e.g., needle pokes, blood on broken skin, blood splash in eye (no sex at work, please)
HBV can survive for 1 week outside the body. Spilled /dried body fluids can be a source of infection.
Keep work areas clean and dry
Prevention: Routine Practice (standard precautions / standard practice) (assume every patient infectious)
HBV vaccine
HBIG (immune globulin) if exposure to infectious material …
passive immunity
Hepatitis C Summary
- Transmission: via blood, less likely by other means – poor sexual transmission
2.Chronic Carriers: common; high risk of cirrhosis or liver cancer down the road
- Risks to HCWs (Health Care Workers) : not well defined; most cases due to needle sticks or sharps injuries
- Prevention: Routine Practice
hepatitis B vaccine does not protect against HCV. No vaccine available - Treatment: interferon and / or combination of new drugs – not suitable for all patients
Viral Replication of HIV
attachment to susceptible host cell
gp 120 (virus) to CD4 receptor site (helper T lymphocytes) / brain cells
fusion to host cell membrane
penetration
reverse transcription (viral RNA → viral DNA)
incorporation of viral DNA into host cell DNA
dormant period (variable); person infected, but no symptoms
replication of viral parts
assembly of viral parts at host cell membrane and release → off to infect new host cells
Effect of HIV on host cell
kills helper T lymphocytes; when number is significantly reduced, get clinical symptoms of AIDS
Diagnoses of HIV
testing for HIV antigens not routine
do screen test for anti-HIV antibodies problems:
takes 4-12 weeks or longer after infection for anti-HIV Ab to appear “negative window” … person infected, but test is negative
can get false positives
if screen test positive, do Western Blot to confirm
Progression of HIV infection
contact
↓
primary infection
(1 month) flu-like symptoms or no symptoms at all
HIV test may be negative
↓
latent period
(about 2 years) no symptoms, but infectious
slow destruction of CD4 cells
HIV test positive
↓
clinical AIDS
variety of opportunistic infections
Cancers (Kaposi’s sarcoma)
Protozoal – Cryptosporidium
Fungal – Candida oral thrush
Viral – shingles
CD4 count < 200
ultimately, death
Treatment of HIV
ZDV - slows viral replication and prolongs latent period, but does not kill virus and does not make new CD4 cells immune to attack; may be given in combination with other antiviral drugs. HAART protocol.
No vaccine available at present
Transmission of HIV
blood is most infectious fluid (but not as infectious as for HBV); other fluids: semen, vaginal secretions, breast milk; virus must make contact with blood or mucous membrane of host
e.g.
sexual intercourse
needle sharing
mom → baby
needle sticks
blood splash on broken skin or mucous membrane
NOT transmitted by: “routine” kissing, touching, casual contact
Risks of HIV to HCWs
accidental needle sticks or sharps injuries
blood splash on broken skin or mucous membrane
handling bloody equipment or clothing … broken skin or mucous membrane
(risk of infection after exposure actually very low)
HCW Prevention for HIV?
Routine Practice
What if HCW HIV positive?
moral, but not legal, responsibility to disclose; little chance of transmitting HIV to patient unless working in area where chance of blood-blood or blood-mucous membrane contact
