MOD4 Blood Borne Pathogens

risk of infection from needle poke without gloves on

HIV — 0.3%

HCV — 3.0%

HBV — up to 30.0% if non-immune

risk of infection from needle poke with gloves on

HIV — 0.15%

HCV — 1.5%

HBV — 15%

whats indicated by the presence of antigens

presence of the actual virus in the body in its infectious state

for most infections: ag = virus = bad news (infectious)

whats indicated by the presence of antibodies

recovery and subsequent immunity 

for most infections: ab = immunity = good news 

whats indicated by the presence of HIV antibodies 

doesnt mean good news — although abs are developed, virus wont be destroyed bcs its hiding inside cells of the cellular immune system

the cells will be destroyed, immune system compromised, results in death 

hepatitis

inflammation of the liver

commonly caused by viral infection of the liver

also caused by alcohol, bacteria, parasites, drugs, chemical toxins, other agents

jaundice

yellow pigmentation of the sclera (eye), skin, brain, etc

caused by liver problems — infected liver isnt able to process the breakdown of erythrocytic products, leads to build up of bilirubin levels in the blood

elevated bilirubin is deposited throughout the body

also gives urine dark amber colour and pale/light stool

hepatitis A virus HAV

small virus without an envelope

infected through ingestion of water/food contaminated w feces 

associated with poor sanitation, personal hygiene and oral-anal sex 

replicates in epithelial lining of oral cavity/intestine > enters circulatory system > invades and replicates in the liver > bile leaving liver carries more HAV into intestine 

incubation period for hep A

15 to 50 days

symptoms of hep A 

usually not evident until two weeks after virus invades liver 

jaundice, pale stool, dark urine 

diagnosis for HAV 

test for antibodies against hep A virus (anti-HAV)

when are feces highly infective for HAV

two weeks before and about one week after the appearance of symptoms

hepatitis B virus HBV 

small enveloped virus — unusually stable 

can resist freezing, moderate heat, some chemical disinfectants 

consists of a nucleic acid core surrounded by protein coat, surrounded by envelope w spikes 

what antigenic areas are associated w HBV

• hep B surface antigen HB_sAg — part of outer envelope

• core antigen HB_cAg

• E antigen HB_eAg

core and E are part of the protein coat

how does HBV replicate in host 

direct entry into blood stream is most efficient 

can also enter through mucous membranes

transported by circulatory system to liver, where virus replicates 

while HBV replicates, virus is carried in blood to other body fluids (blood, saliva, spinal fluid, tears, urine, semen, vaginal secretions, mothers milk)

asymptomatic infections for HBV

most ppl infected w HBV (60-70%) will have no disease symptoms and wont be aware of it unless tested for hep B antigens

symptomatic infections for HBV

majority will experience symptoms of 2w to 6m after exposure

average incubation period is 3m

symptoms: infl of liver, malaise, anorexia, nausea, vomiting, abdominal discomfort, jaundice

fulminant infections

rapid, severe, sudden

seen in 1-3% of infected individuals

usually young people w good immune system

if majority of liver cells are infected, cell destruction from T cells will cause complete liver failure — will enter hepatic coma and may cause death, needs transplant

HBV carriers 

5-10% of infected ppl will become carriers — even if asymp

• reservoir of HBV — certain body fluids are infectious for 6-7 years

• chronic viral infection of liver cells predisposes pts to primary hepatocellular carcinoma 

transmission of HBV

through infected blood — minute amounts needed to infect

• shared needles for drugs

• sexual activities w blood exposure

• tattoo/acupuncture/electrolysis w shared needles

• shared razors, toothbrushes

• needle sticks

• blood spilled on broken skin

infective in blood spills for up to one week at room temp — blood-stained clothes/bandages

what antigen is tested for when diagnosing HBV

HB_sAg — surface antigen, first appears in sample abt 2 months after exposure, level inc rapidly for abt a month, symptoms are evident 

replication of virus diminishes, amt of antigen decreased

abt 5 months, lvl is undetectable 

w/in few weeks, anti HB_s antibodies will appear — recovery 

anti HB_s

hep B surface antibodies

produced by pt in response to surface antigen

indicates pt is recovering from HBV or has been immunized

anti HBc

hep B core antibodies

produced by pt in response to core antigen

diagnostic test for HBV during convalescent window

HB_eAg

hep B e antigen 

part of inner protein coat of the virus

indicates all body fluids are infectious 

anti HBe

hep B e antibodies

produced by the pt in response to e antigen

indicates pt is clearing e antigen and becoming less infective 

preventative measures for hep B

• routine practices — PPE

• hep B immunization — many healthcare orgs require vaccine against HBV

• hep B immune globulin — HBIG available for short-term prevention when healthcare indiv exposed to infectious material, administered w/in 48hrs

hepatitis C virus

approx 20% of all cases of acute hepatitis

associated w intravenous drug abuse

found in blood

hepatitis D virus HDV

defective RNA virus that can only replicate in presence of HBV

associated w progressive liver damage and fulminant hepatitis 

spread in blood, semen, vaginal secretions

whats the best protection against HDV

immunization aaginst HBV — HDV cant infect liver cells w/out presence of HBV

hepatitis E

spread fecal-oral route

esp serious for pregnant females

HIV

infection w virus — asymptomatic

enveloped RNA retrovirus w glycoprotein spikes

AIDS

clinical symptoms evident

components of HIV

core

• center of virus

• two strands of RNA

• reverse transcriptase enzyme used to produce viral DNA from RN

protein coat

• surrounds core

• consists of proteins

lipid envelope

• lipid bilayer, glycoprotein spikes protrude out — lollipop!

• candy pt of lollipop is gp120

• responsible for binding virus to host cell 

hardiness of HIV

not very hardy — use routine sterilization, disinfection and cleaning methods to inactivate virus