Term
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Definition
how to determine transmission? 1. through understanding the biology of HIV and 2. from collecting empirical epidemiological evidence
HIV (either free virus or cells infected with virus) must cross the epithelial barriers into the fluid compartments of body (relatively difficult to due with most viruses) |
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Term
| Sources of HIV for Transmission |
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Definition
1. cells infected with a provirus - macrophages and T-cells
-macrophages: primary source, first cells infected, long-term, circulate through bloodstream. found in all mucous linings (internal urogenital surfaces of vagina and penis, lining of anus, lungs, and throat).
-T-cells
2. fluids and secretions
-free HIV, infected macrophages and T-cells found in:
*blood (1,000-100,000 HIV/microliter)
*semen (10-50 HIV/ml)
*vaginal and cervical secretions (menstrual fluid)
*breast milk
- also in saliva, tears and urine. but in very low amounts (<1 HIV/ml) so they are not transmission sources |
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Term
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Definition
-for transmission to be successful, HIV must survive long enough to contact a susceptible person and target host cells
-HIV is a fragile virus outside of host
-within host HIV is active 1.5 days
-outside of host HIV is active 6 hours
-HIV is inactivated by desiccation (drying), light, soap and water |
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Term
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Definition
-# of infectious virus particles required to cause infection
-don't know for sure but...
-study at University of Alabama: 76% infected with just 1 HIV particle and 24% infected with 2-5 HIV particles. OMG!!!! |
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Term
| Modes of Transmission: Casual Contact |
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Definition
NOT
-no measured association between HIV transmission and shaking hands, hugging, kissing, phone use, pool use, sharing utensils, toilet, or household items
-1 case study of kissing causing transmission BUT it was deep kissing and both partners had periodontal gum disease and open bleeding mouth sores. bleh! |
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Term
| Modes of Transmission: Insect Vector |
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Definition
NOT
-a parasite multiplies in host and concentrates itself in the salivary glands. when vector takes a blood meal, parasites pass to the victims blood through the saliva.
-HIV cannot multiply in insects and HIV cannot survive in salivary glands. there's no way to exit the insect because mosquitos suck blood but don't inject blood
-also, mosquitos wash their proboscis so only 1/1000 of blood is left on the proboscis needle (not enough for transmission into next host) |
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Term
| Modes of Transmission: Perinatal |
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Definition
YES
1. In utero - brings source of HIV/cells (blood of mother) and potential target (blood of fetus) in a protected environment (womb)
-placenta - separated the mother and child's blood. allows exchange of nutrients but not actual cells
-however, during 3rd trimester, small tears can occur in the placenta allowing for exchange of blood :(
2. Birth - during birth, child comes into contact with mother's blood and vaginal secretions and could swallow it (baby has no immune system so HIV can enter child's body from ingestion)
-30% chance that child will be infected
-this is why C-section is thought to be safer (controlled bleeding)
3. Infected breast milk - contains lots of CD4 cells
-poverty increases transmission to babies because mothers have no choice but to breast feed |
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Term
| Modes of Transmission: Blood Transfusion |
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Definition
YES
-placing blood or blood products directly into bloodstream of another person
-18 million units of blood transfused per year in US
-1984 (no blood screening tests) risk of receiving HIV infected blood was 40/100,000
-now the risk is 2.25/100,000
-because screening tests are not perfect and blood could be donated during seroconversion (infection -> a measurable amount of anti-HIV antibodies) |
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Term
| Modes of Transmission: Injecting HIV-Infected Blood |
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Definition
1. IV drug use - needle sharing
-user will draw blood into syringe to find the vein, then inject the drug+blood. so after, the needle and syringe contains small amounts of HIV and cells. so the next user is contaminated with HIV, etc
-sharing occurs over a short time allowing HIV to live
-barrel and needle provide a protective environment for HIV (no light, no drying)
2. Accidental needle sticks
-in health care setting: low risk, but still some risk
- of 1,031 people accidentally stuck with needles, 4 became HIV+ and of 141 exposure to mucous membrane or wound contamination, 0 became HIV+ |
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