HIV Flashcards
HIV significance
Number of new cases/year in US has been consistent at 40,000 for several years.
Now see growing rates among women, people of color, poor people and adolescents.
Men having sex with men (MSM) still accounts for most cases in the US and Canada.
There have been major advances in treatment to keep HIV infected people healthy for longer periods of time so the death rate has fallen.
In developing countries the major route of transmission has been heterosexual sex with women and children bearing a large part of the burden of illness.
At the end of 2004 statistics showed:
a. 39.4 million people, including 2.2
million children under 15, were
living with HIV.
b. 3 million died with HIV related causes
transmission of HIV
HIV is a fragile virus and can only be transmitted under specific conditions that allow contact with infected body fluids like blood, semen, vaginal secretions and breast milk.
Transmission of HIV occurs through sexual intercourse with an infected person, exposure to HIV infected blood or blood products, and through perinatal transmission during pregnancy, during time of delivery and through breast feeding.
transmission of HIV (cont.)
HIV infected people can transmit HIV to others within a few days. Often that ability is life-long.
There has to be enough of the virus that enters a susceptible host. The viral load (HIV in a ml. of serum) is variable in blood,
semen, vaginal secretions and breast milk.
Large amounts of HIV can be found in blood during the 1st 6 months of infection and during the later stages of disease.
Can not be spread casually by hugging, dry kissing, shaking hands, sharing eating utensils, using same toilet seat, or attending school or work with infected person.
Is not transmitted through tears, saliva, urine, emesis, sputum, feces or sweat.
The primary way health care workers get infected is by needle sticks with infected blood but there is a low risk for contracting HIV.
sexual transmission HIV
Unprotected sex with a HIV infected person is the most common type of transmission.
MSM (males having sex with males) still accounts for most cases in the US & Canada.
Heterosexual transmission is becoming more prevalent and is most common cause for women.
During any form of sexual intercourse, the risk for infection is greater for the person receiving the semen because there is prolonged contact with the infected fluid.
Sexual activities that involve blood ( period or trauma to local tissues ) increases the risk of transmission.
The presence of genital lesions from sexually transmitted diseases (STDs) significantly increases the risk of transmission.
Contact with Infected Blood or Blood Products
HIV can be transmitted from exposure to infected blood through injection drug use (IDU) as in using contaminated equipment or sharing equipment that is infected.
Blood transfusions account for only 1% of cases because of the thorough testing that occurs now. Clotting factors used by people with Hemophilia is now treated with heat and chemicals that kill HIV.
Puncture wounds are the most common work related causes of HIV infection but risk is about 3 to 4 per 1000. The risk will be higher if the infected person has a high viral load at the time of transmission.
Splash exposures to blood or skin with an open lesion have some risk but is less than a deep puncture exposure.
perinatal transmission
Infection from an infected mom to the infant can occur during pregnancy, at the time of delivery and through breast feeding.
It is the most common route of transmission to children.
Because antibodies are transmitted from the mom to the fetus, all infants test positive for HIV at birth. Ongoing testing of the infant is needed to determine if the infant is really infected with HIV. Therefore they are not routinely treated with antiretroviral drugs (ARTs) until there is a definite diagnosis of HIV.
Only 25% of infants born to untreated HIV infected moms develop HIV. If the mom is under treatment, the risk drops to 2%.
pathophysiology of HIV
HIV is a RNA virus that is a retrovirus because it replicates in a backward manner going from RNA to DNA.
HIV can’t replicate unless in a living cell. Can enter when “knobs” on viral envelop bind to specific CD4 receptor sites and then is able to enter CD4 T cells.
RNA is transcribed into a single strand of DNA with reverse transcriptase, an enzyme made by the retrovirus.
pathophysiology of HIV cont
Strand copies itself becoming a double stranded viral DNA which enters a cell’s nucleus and using the enzyme integrase splices itself into the genome and becomes a permanent part of the cell’s genetic structure.
Consequences are:
1. Because genetic material is replicated during cell division, daughter cells will also
be infected.
2. Viral DNA will direct cell to make new HIV.
HIV production starts with long strands of HIV RNA.
It is then cut into appropriate lengths in the presence
of protease.
pathophysiology of HIV cont.
The initial HIV infection results in viremia ( large amounts of virus in the blood). Is followed within a few weeks by prolonged period where HIV levels in the blood remain low even without treatment. May last 10 to 12 years with few symptoms. Still, HIV replication occurs at rapid and constant rate in the blood and lymph.
A major consequence of rapid replication is that copy errors can occur causing mutations that make it difficult to treat and to make a vaccine.
pathophysiology of HIV cont.
In normal immune response, foreign antigens interact with B & T cells. In initial stages of HIV infection, these cells respond and function normally.
HIV infects the CD4 receptors on lymphocytes, monocytes, macrophages, astrocytes, and oligodendrocytes.
HIV damages CD4T cells which have a key role in the ability of T cells to recognize and defend against pathogens. HIV destroys CD4T cells.
pathophysiology of HIV cont.
Bone marrow & thymus are able to produce enough CD4 cells to replace the destroyed ones for many years.
Eventually, HIV destroys more than can be replaced. Generally, the immune system will remain healthy with more than 500 CD4T cells/ul. Severe problems result when levels fall below 200 CD4T cells/ul.
Major concern R/T immune suppression is the development of opportunistic diseases ( infections & cancers).
clinical manifestations of HIV
Disease progression is highly individualized and treatment can alter this pattern. Usual stages are:
1. Acute Infection 2. Early Chronic Infection 3. Intermediate Chronic Infection 4. Late Chronic or AIDS
Acute infection (HIV)
The development of HIV specific antibodies
(seroconversion ) is frequently accompanied
by flulike symptoms ( fever, swollen lymph
nodes, sore throat, headache, malaise,
nausea, diarrhea, muscle/joint pain & diffuse
rash.
Some people have neurological complications like aseptic meningitis, peripheral neuropathy, facial palsy, & Gillian Barre’.
Acute infection stage generally starts 1 to 3 weeks after initial infection and lasts 1 to 2 weeks.
early chronic infection (HIV)
The median interval between untreated HIV and the diagnosis of AIDS is about 11 years.
During the Early Chronic phase the CD4T cell lymphocytes are above 500 cells/ul and the viral load is low.
Referred to as asymptomatic disease although fatigue, headache, low-grade fever, night sweats, and persistent generalized lymphadenopathy may occur.
Patient may not be aware they are HIV infected. They can transmit HIV infection.
intermediate chronic infection (HIV)
CD4T cell count drops to 200 to 500 cells/ul and viral load increases. HIV advances to more active stage.
Symptoms of earlier stage worsen.
Patient may have chronic diarrhea, persistent fever, frequent drenching night sweats, recurrent headache and fatigue severe enough to interrupt normal routine.
May have local infections like Candidiases or thrush. Candida rarely causes problems in healthy persons but will occur in HIV persons.
