Download Human immunodeficiency virus (HIV)

ARO Training & Consulting
Bloodborne Pathogens
Module 4: Human Immunodeficiency Virus (HIV) Exposure
Page 36
Objectives:
1.
2.
3.
Describe the routes of transmission associated with HIV infection.
State the prevalence of HIV infection in the population.
Describe the incubation period preceding seroconversion in individuals
exposed to HIV.
4. Describe the incubation period preceding symptoms of HIV infection.
5. Describe the complications associated with chronic HIV infection.
6. Discuss the risk of developing HIV infection following exposure.
7. Describe safety measures associated with prevention of HIV exposure.
8. Describe safety measures associated with prevention of HIV infection
following exposure.
9. Describe the current role of immunization with respect to prevention of
HIV infection.
10. Be familiar with the treatment for HIV.
11. Describe the role of prophylactic treatment following exposure to HIV.
12. Be familiar with the differences between HIV screening tests and
confirmatory tests, and with the problems associated with false-positive
and false-negative results.
ARO Training & Consulting
Bloodborne Pathogens
Module 4: Human Immunodeficiency Virus (HIV) Exposure
Page 37
Introduction
The human immunodeficiency virus (HIV) was first discovered in 1983. HIV is
responsible for causing autoimmune deficiency syndrome (AIDS). HIV attacks
the body’s immune system, leaving the host susceptible to opportunistic
infections. The incidence of occupationally acquired infection with HIV is
relatively low, but needle-stick exposure during phlebotomy procedures presents
a serious potential hazard. There is no vaccine to protect against HIV infection,
and currently there is no cure.
There are two types of HIV: HIV-1 and HIV-2. HIV-2 occurs most commonly in
Western Africa, and is uncommon in North America.
Retroviruses
HIV is a Retrovirus, and like HBV and HCV, relies on the production capabilities
of host cells to replicate itself. However, unlike HBV and HCV, which infect liver
cells, HIV infects T-cells (specialized lymphocyte), monocytes and macrophages
– types of white blood cells that our immune systems produce to help fight
infection.
During the viral replication process inside the T-cells, genetic material from the
virus is integrated in the host’s genetic material, and may remain inactive (latent)
for 3-10 years.
Once incorporated in the host cell DNA, each time a cell divides, viral genetic
material is passed on to the two daughter cells, so that once a cell is infected, all
descendents of that cell will also be infected.
During the latent phase, the virus remains inactive (dormant). If the cell does not
become activated, the virus remains dormant. If the infected cell dies before it
divides again, and before it becomes activated (T4-cells live only a few days
while monocytes/macrophages live for weeks to months), the virus will be
degraded along with the rest of the cell’s DNA, and the number of HIV-infected
cells will decrease and could even disappear. However, it is unlikely that T4-cells
and monocyte/macrophages will die before becoming activated, as their purpose
is to become activated in response to foreign substances entering the body.
When the cell is activated or turned-on, the process resulting in virus replication
begins. New viral particles are released through the host cell membrane
(budding) to infect other host cells. The replication process damages or kills
infected helper T-cells; however, infected monocytes usually survive and become
reservoirs of infective virus.
ARO Training & Consulting
Bloodborne Pathogens
Module 4: Human Immunodeficiency Virus (HIV) Exposure
Page 38
Unless the HIV lifecycle is interrupted by treatment, the virus infection spreads
throughout the body and results in the destruction of the immune system. With
current anti-viral medications, HIV infection can be contained for a period of time;
however, there is currently no cure for HIV infection and sooner or later immune
deficiency occurs (AIDS).
For more information on HIV pathogenesis.
Link to http://www.critpath.org/aric/library/path.htm
Epidemiology
Global
The World Health Organization reported at the end of 2003 that there were
approximately 40,000,000 people living with HIV and/or AIDS worldwide. Most
cases (95%) occurred in low and middle-income countries.
Five million of these were new HIV infections that occurred during 2003 –
approximately 14,000 new HIV infections each day. In the same year, a total of
3,000,000 people died of HIV and AIDS related causes.
Geographic Distribution
Approximately 70% of HIV infections occur in individuals in Sub-Saharan Africa,
followed by 15% in South and South-East Asia. Only 2.5% of HIV infections
occur in North American individuals.
Globally, nearly 2% of all new HIV infections are caused by unsafe injections with
a total of 96,000 people infected annually. In South Asia up to 9% of new cases
may be caused by unsafe injections.
As was mentioned in Module 1, reuse of unsterilized or improperly sterilized
syringes and needles exposes millions of people to infection.
United States
The CDC estimated that currently there are approximately 200,000 persons in
the U.S. living with HIV infection, and another 800,000 persons with HIV infection
that has progressed to AIDS.
Of these, the majority of cases are seen in men (~80%); however, the occurrence
is increasing in women, especially among IDU.
http://www.cdc.gov/hiv/stats.htm#data
ARO Training & Consulting
Bloodborne Pathogens
Module 4: Human Immunodeficiency Virus (HIV) Exposure
Page 39
Approximately 48% of all HIV/AIDS infected individuals in the U.S. live in the
following States (listed in order of prevalence):
-
New York
California
Florida
Texas
Race/Ethnicity distribution
HIV/AIDS infection is increasing most rapidly among minority populations and is
a leading killer of African-American males aged 25-44 years. AIDS affects ~ 7
times more African Americans and 3 times more Hispanics than whites.
Exposure category distribution
Approximate distribution of individuals with HIV/AIDS in the U.S. by exposure
category:
-
men who have sex with men (MSM) – 40%
IDU – 24%
MSM/IDU – 5%
Heterosexual contact – 30%
Not identified – 2%
For further information on HIV infection in the U.S. Link to –
http://www.cdc.gov/hiv/pubs/facts.htm
Canada
Health Canada estimated that 56,000 Canadians were living with HIV infection
and/or AIDS in 2002, and that approximately 30% of those infected did not yet
know they are infected. The undiagnosed group is important, because they may
unknowingly spread the HIV virus, and until diagnosed, cannot receive treatment
and counselling.
In Canada, risk groups for HIV and AIDS are:
-
Aboriginal people
Injection drug users (16 - 23.9% of HIV infections)
Men who have sex with men (up to 70%)
Women (~ 8 %)
Youth (~ 3 %)
Although Aboriginal groups represent only 3.3% of the Canadian population, they
are at high-risk for HIV infection (due to poverty, substance abuse, sexually
transmitted diseases, and limited health-care access).
ARO Training & Consulting
Bloodborne Pathogens
Module 4: Human Immunodeficiency Virus (HIV) Exposure
Page 40
In addition, HIV infection among women is also increasing, due largely to
substance abuse.
For further information on HIV infection in Canada, Link to Health Canada
Website - http://www.hc-sc.gc.ca/english/diseases/aids.html
Discrimination and stigma
A survey performed by Health Canada indicates that stigma and discrimination
associated with HIV/AIDS still persist in Canada:
-
30% of adult Canadians would be uncomfortable working in an office with
a person with HIV
40% would be uncomfortable if their child was attending a school where
one of the students had HIV/AIDS
> 50% would be uncomfortable if a close friend or relative were dating
someone with HIV/AIDS
~ 50% of Canadians believe that people living with HIV/AIDS should not
be allowed to serve the public in positions such as cooks and dentists
A survey of 50 people with HIV/AIDS in New Brunswick found that ~ 30% of
those surveyed reported being rejected by family and friends in 2000.
A recent survey of 34 people with HIV/AIDS in Alberta indicated that ~ 30%
reported being treated unfairly by employers or co-workers as a result of their
HIV status.
ARO Training & Consulting
Bloodborne Pathogens
Module 4: Human Immunodeficiency Virus (HIV) Exposure
Page 41
Transmission
Human immunodeficiency virus (HIV), the virus that causes acquired
immunodeficiency syndrome (AIDS), is transmitted through sexual contact,
exposure to infected blood or blood components, and perinatally from mother to
newborn. Risk factors are:
-
-
unprotected sexual intercourse – entry through the lining of the vagina,
vulva, penis, rectum or mouth during sex
sharing of needles and IV drug equipment
infected mother to infant
o during pregnancy
o during delivery
o during breast feeding
treatment with blood and blood products prior to national screening
initiatives
occupational exposure
o health care workers
o emergency responders (fire, ambulance, etc.)
o law officers
o prison guards
HIV has been recovered from the following body fluids:
- blood
- semen
- vaginal secretions
- saliva
- tears
- breast milk
- cerebrospinal fluid
- amniotic fluid
- urine
Despite the range of body fluids that HIV has been recovered from, only blood,
semen, and vaginal secretions have been implicated in the transmission of HIV.
The risk of HIV transmission through breast milk, CSF, synovial fluid, pleural
fluid, peritoneal fluid, pericardial fluid, and amniotic fluid has not yet been
determined.
ARO Training & Consulting
Bloodborne Pathogens
Module 4: Human Immunodeficiency Virus (HIV) Exposure
Page 42
Occupational Exposure
A significant occupational exposure that may place a worker at risk of HIV
infection is defined as a percutaneous injury, contact of mucous membranes, or
contact of skin (especially when the exposed skin is chapped, abraded, afflicted
with dermatitis, or the contact is prolonged or involves an extensive area) with
blood, tissues, or other body fluids (semen, vaginal secretions, other body fluids
contaminated with visible blood, CSF, synovial fluid, pleural fluid, peritoneal fluid,
pericardial fluid, and amniotic fluid, and laboratory specimens and preparations
(e.g., suspensions of concentrated virus) that contain HIV.
Occupational HIV Transmission
Risk to Health-Care Workers
Transmission of HIV following occupational exposure appears to be related to a
number of factors. Morbidity Mortality Weekly Report (MMWR), a publication of
the Centers for Disease Control and Prevention (CDC), reported three factors
associated with seroconversion among workers who received occupational
exposures to HIV:
-
-
volume of blood injected (deep injury, procedure involving needle placed
directly into source patient's vein or artery, visible contamination of sharp
with patient's blood)
terminal HIV illness in source patient due to high levels of circulating virus
lack of post-exposure prophylaxis
Reference: Case-Control Study of HIV Seroconversion in Health-Care Workers After
Percutaneous Exposure to HIV-Infected Blood -- France, United Kingdom, and United
States, January 1988-August 1994. Retrieved from
http://www.cdc.gov/mmwr/preview/mmwrhtml/00039830.htm on August 14, 2004.
Evidence also suggests that host defences of an individual influence the risk for
HIV infection following exposure to HIV infected blood. Under the same
circumstances involving exposure to two individuals, one may develop infection
while the other does not. It is likely that differences in individual immune
response affect the risk of whether an individual who is exposed to the HIV virus
actually becomes infected.
ARO Training & Consulting
Bloodborne Pathogens
Module 4: Human Immunodeficiency Virus (HIV) Exposure
Page 43
Percutaneous injury (sharps)
Although the risk of seroconversion following needle-stick injury involving HIVpositive body fluids is low, the potential is real, with about one seroconversion for
every 200 - 300 needle-sticks. The rate of transmission of HIV is considerably
lower than that for HBV, possibly due to the lower concentrations of virus in the
blood of HIV-infected patients.
Reference: Centers for Disease Control and Prevention (CDC). (1989). Guidelines for
Prevention of Transmission of Human Immunodeficiency Virus and Hepatitis B Virus to
Health-Care and Public-Safety Workers A Response to P.L. 100-607 The Health
Omnibus Programs Extension Act of 1988. MMWR; 38(S-6);3-37. Retrieved from
http://www.cdc.gov/mmwr/preview/mmwrhtml/00001450.htm on August 14, 2004.
Mucous membrane exposure
The risk of seroconversion
approximately 0.09%.
following
mucous
membrane
exposure
is
Non-intact skin exposure
HIV transmissions following exposure of non-intact skin to blood have been
documented, but the average risk of seroconversion has not been determined. It
is expected that the risk of infection following exposure of non-intact skin to body
fluids from patients infected with HIV is less than the risk following mucous
membrane exposure.
Exposure to body fluids and tissues
The risk of transmission after exposure to fluids or tissues other than HIVinfected blood has not been quantified, but is likely even lower than the
probability associated with exposure to blood.
HIV infection in healthcare workers (HCWs) has been attributed to needle-stick
exposures to blood from HIV infected patients, extensive contact with blood or
other body fluids in the absence of barrier precautions, and direct contact of skin
with blood from infected patients (skin lesions present), and mucous-membrane
exposure. The risk of exposure of non-intact skin or mucous membranes is likely
to be much less than that from percutaneous exposure.
As of June 2000, the CDC had received 56 voluntary reports of HCW with
documented seroconversion associated with occupational exposure to HIV in the
U.S. An additional 138 HIV transmissions in HCW were considered possible
occupational HIV transmissions. Although there was a history of occupational
exposure to blood, other body fluids or laboratory solutions containing HIV, and
no other identified risk for HIV infection in these 138 possible occupational
transmissions, a single specific exposure was not associated with HIV
seroconversion.
ARO Training & Consulting
Bloodborne Pathogens
Module 4: Human Immunodeficiency Virus (HIV) Exposure
Page 44
In 1996, the first documented occupational transmission of HIV in Canada clearly
linked to a specific incident occurred in a HCW in British Columbia. The HCW,
who was not wearing gloves at the time, received a puncture wound while caring
for a person with advanced HIV disease.
Two other cases of possible occupational transmission of HIV have also been
reported in Canada. Both involved laboratory workers.
For further information Link to Health Canada - http://www.hc-sc.gc.ca/pphbdgspsp/publicat/ccdr-rmtc/96vol22/dr2207ec.html
Risk to Emergency Responders and Public Safety Workers Acquiring HIV
in Health-Care Settings
Emergency medical technicians (EMTs)
In the U.S., one study documented 115 occupational exposures among firstresponder subgroups with 84% occurring in emergency medical technicians
(EMTs).
In another study of a city-wide EMT work-force, 472 body fluid exposures were
documented in 1400 patient encounters. Personal protective equipment
prevented skin or face contact in 87% of these exposures.
Police officers
A study involving police officers found that 33 of 111 exposures were significant.
Of the 29 sources, 3 individuals were documented HIV antibody positive.
Although no seroconversions in exposed officers occurred, the potential for
transmission exists.
Correctional facility workers
Another survey of 2215 correctional facility workers found that 88 of 149
exposures occurred in the medical/dental units.
Reference: Int Conf AIDS 1991 Jun 16-21; 7:425 (abstract no. W.D.4150) Strine PW,
Martin LS, Mullan RJ; Centers for Disease Control, National Institute for Occupational
Safety and Health, HIV Activity, Atlanta, GA
Future trends
The increasing prevalence of HIV increases the risk that HCWs will be exposed
to blood from patients infected with HIV, especially when standard precautions
are not followed for all patients.
HCWs must consider ALL patients as potentially infected with HIV and/or other
blood-borne pathogens and adhere to infection-control precautions for minimizing
the risk of exposure to blood and body fluids of all patients.
ARO Training & Consulting
Bloodborne Pathogens
Module 4: Human Immunodeficiency Virus (HIV) Exposure
Page 45
HIV disease progression
Infection with HIV-1 results in a progressive loss of immune function, which
ultimately leads to opportunistic infections and malignancies associated with
acquired immunodeficiency (AIDS).
Currently, 5 stages of illness are recognized:
Acute infection (seroconversion)
Early disease
Middle stage disease
Late disease
Advanced disease
Acute HIV infection (Seroconversion)
Acute HIV infection may also be referred to as acute retroviral seroconversion
syndrome.
The acute phase of HIV infection refers to the period from initial infection until the
immune response demonstrates some control over viral replication, lasting from
a few weeks to a few months.
Symptoms usually occur within 2 – 6 weeks following exposure and usually
disappear within one week to one month.
Many individuals do not have symptoms or may have mild flu-like symptoms
when they are first infected with HIV and initial infection is often not recognized.
Only 20 – 30% of symptomatic individuals seek medical attention, and when they
do symptoms are often mistaken for other viral infections.
If present, symptoms are nonspecific and temporary - fever, malaise, rash,
lymphadenopathy, pharyngitis, headache, and diarrhea.
Acute infection is characterized by active viral replication and extremely high
levels of circulating virus in the blood. At this point, people are very infectious and
HIV is present in large quantities in genital fluids. During the acute phase, the
virus spreads throughout the body and seeds lymphoid tissues, where replication
is partially suppressed.
Seroconversion generally occurs 2-3 months following HIV exposure.
ARO Training & Consulting
Bloodborne Pathogens
Module 4: Human Immunodeficiency Virus (HIV) Exposure
Page 46
Early disease (Asymptomatic)
With the exception of mild to moderate lymphadenopathy and skin conditions
(dermatitis, psoriasis, dry skin, fungal infection, etc.), there are generally no
symptoms related to HIV infection.
This asymptomatic phase of the disease is referred to as the clinically latent
period of HIV infection due to the absence of symptoms suggesting that,
although the virus is present, it is inactive at this point.
This is the longest stage of HIV infection, responsible for approximately 80% of
the total disease course.
Middle Stage Disease
Most individuals remain asymptomatic or mildly symptomatic during this period.
Skin conditions persist and may worsen, and mouth ulcers and lesions may
appear or worsen.
Other disorders begin to appear during the middle stage of disease – herpes
simplex, varicella-zoster virus (shingles), oral or vaginal candidiasis, oral hairy
leukoplakia, recurrent seborrhea and other skin disorders, recurrent diarrhea,
intermittent fever, and unexplained weight loss (> 10 pounds in 6 – 8 week
period).
Other symptoms including muscle and joint pain, headache and fatigue may also
be present during this stage.
Routine bacterial infections such as sinusitis, bronchitis and pneumonia are more
common, as well as tuberculosis, syphilis, herpes infection and lymphoma.
Late Disease – AIDS
The early presentations of AIDS include generalized enlargement of lymph
nodes, fever, chronic fatigue, weight loss, and in some cases thrombocytopenia.
The disease gradually progresses and late presentations include increased
susceptibility to opportunistic infections, predisposition to malignant tumors,
central nervous system damage, and general weakening of the body.
During this state of infection, large numbers of viral particles are present in blood
and body fluids.
As the disease progresses, the rate of loss of T-cells increases. HIV over time
will usually succeed in reducing the available number of T-cells to very low
levels, increasing the risk of opportunistic infections and malignancies that may
be life threatening.
ARO Training & Consulting
Bloodborne Pathogens
Module 4: Human Immunodeficiency Virus (HIV) Exposure
Page 47
During the late stage of disease, lymphoid tissue is destroyed, resulting in the
loss of virus-trapping capability and contributing to severe immune deficiency.
Infected individuals are at high risk for developing life-threatening opportunistic
infections and malignancies.
Approximately 6% of HIV-infected individuals show rapid disease progression,
experiencing a rapid decline in T-cell counts within 2 to 3 years, and developing
full-blown AIDS within 3 years of acute HIV infection.
Advanced HIV Disease
Prior to current treatment programs, individuals with advanced HIV disease were
likely to develop a new AIDS-defining illness and/or die within 2 years of
progressing to AIDS.
Certain opportunistic infections are associated with advanced stages of
immunosuppression – Mycobacterium avium complex infection, meningitis
caused by Cryptococcus, invasive fungal infections (i.e. aspergillosis and
histoplasmosis), and wasting (loss of > 10 lb. of usual body weight). Typically,
multiple disease conditions coexist. Retinitis caused by the cytomegalovirus
(CMV) is the leading cause of blindness in advanced HIV disease.
Individuals with advanced disease are living much longer than in the early years
of the AIDS epidemic due to aggressive antiretroviral therapy and earlier
identification and treatment of opportunistic infections. Recent statistics indicate
that AIDS-related deaths among all AIDS cases have decreased.
ARO Training & Consulting
Bloodborne Pathogens
Module 4: Human Immunodeficiency Virus (HIV) Exposure
Page 48
Complications of AIDS
-
Infections
Malignant tumors
Damage to nerves, muscles, spinal cord
AIDS dementia - cognitive and memory impairment, and impaired ability to
concentrate and perform complex tasks
Wasting syndrome (general weakening and degeneration of the body)
Laboratory Testing
Diagnosis
HIV is diagnosed by screening blood for antibodies to the virus. If the body is
making antibodies to HIV, then the body has been exposed and probably is
infected with the virus. Antibodies to the HIV virus are usually detectable within 23 months following infection, but may take longer (up to 14 months).
False-positive and false-negative HIV-antibody reactions have been reported.
False positive results occur when HIV antigens used in testing cross-react with
antibodies in the patient’s serum produced against antigens unrelated to HIV.
Initial positive test results are confirmed by additional testing.
Presence of antibodies to the HIV virus indicates that a person has been
exposed to the virus and has mounted an immunologic response (serum
antibodies). However, antibody testing does not indicate whether the individual
currently harbours the virus, although current evidence related to retroviruses
suggests that most, if not all, HIV-antibody positive individuals will remain
indefinitely infected.
HIV Vaccine
Currently, no HIV/AIDS vaccines are approved for use; however, many are in
clinical trial studies.
For information on vaccine clinical
http://www.aidsinfo.nih.gov/vaccines/
trial
studies
in
progress
-
ARO Training & Consulting
Bloodborne Pathogens
Module 4: Human Immunodeficiency Virus (HIV) Exposure
Page 49
Treatment
The Canadian Youth, Sexual Health and HIV/AIDS Study demonstrated that
approximately 67% of Grade 7 students and 50% of Grade 9 students in Canada
do not know that there is no cure for HIV/AIDS.
Although most Canadian adults recognize that HIV/AIDS is a serious problem,
close to 20% believe that it can be cured if treated early, and they perceive their
own personal risk of HIV infection to be low.
Reference: Link to HIV/AIDS: Responding to a changing epidemic. - http://www.hcsc.gc.ca/hppb/hiv_aids/report03/wad2.html
There is still no cure for AIDS — prevention is the only protection against AIDS at
this time, and for people living with HIV/AIDS, treatment failures are becoming
more common as new strains of the virus appear and the human body develops
resistance to HIV/AIDS drugs.
Guidelines for the treatment of HIV infection include recommendations for the
use of three drugs. Because of the ability of HIV to remain in some latently
infected cells and the lack of therapeutic agents that target latently infected cells,
patients must remain on anti-viral therapy for life.
The current goal of HIV treatment is to completely suppress viral replication for
as long as possible with periodic determination of the number of virus particles in
the blood to measure response to therapy.
Treatment most commonly involves combination antiretroviral therapy for
patients in the early or middle stage of disease.
Future directions
One immediate goal in HIV treatment is to design new, more potent medications
that are easier to take and have fewer side effects.
As our understanding of the HIV lifecycle improves, the ability to develop
medications to cure HIV infection and create a vaccine that will prevent infections
from occurring is the hope for the future.
Side effects of anti-HIV medications
Side effects related to the drugs used for treatment are common and may be
severe. In addition, drug resistance may occur especially if drugs are not taken
as prescribed.
ARO Training & Consulting
Bloodborne Pathogens
Module 4: Human Immunodeficiency Virus (HIV) Exposure
Page 50
Post Exposure Prophylaxis (PEP)
Post exposure prophylaxis is short-term antiretroviral treatment to reduce the
likelihood of HIV infection after potential exposure, either occupationally or
through sexual intercourse.
Although the risk of seroconversion following needle-stick injury involving HIVpositive body fluids is low, the risk is real (1 seroconversion in every 200 to 300
needle-stick injuries).
Occupational exposure to an HIV-infected individual should be considered an
urgent medical concern. Information about primary HIV infection suggest that
systemic infection does not occur immediately, leaving a brief window of
opportunity during which post-exposure antiretroviral treatment might reduce or
prevent viral replication. Theoretically, initiation of antiretroviral PEP soon after
exposure might prevent or inhibit systemic infection by limiting the replication of
virus in the initial target cells or lymph nodes.
Post-exposure treatment guidelines (CDC, 2001)
Recommendations for treatment following exposure to HIV include a 4-week
regimen of two different classes of drugs.
An expanded treatment regimen includes the addition of a third drug for HIV
exposures that pose an increased risk for transmission.
When the source virus is known or suspected to be resistant to one or more of
the drugs considered for the PEP regimen, the selection of drugs to which the
source person’s virus is unlikely to be resistant is recommended.
Reference: U.S. Department of Health and Human Services. 2001. Updated U.S. Public
Health Service Guidelines for the Management of Occupational Exposures to HBV,
HCV, and HIV and Recommendations for Postexposure Prophylaxis. MMWR;50(RR-11)
http://www.aidsinfo.nih.gov/guidelines/health-care/HC_062901.pdf
Toxicity Associated with PEP has been reported - nearly 50% of HCW
experience adverse symptoms that include symptoms of nausea, malaise,
headache, anorexia and headache while taking PEP. Approximately 33% of
HCW stop taking PEP because of adverse signs and symptoms.
Serious side effects, including hepatotoxicity, kidney stones, hepatitis,
pancytopenia and serious skin disorders have also been reported with the use of
combination drugs for PEP.