The human immunodeficiency virus (HIV) targets the immune
system and weakens people's defense against many infections and some types of
cancer that people with healthy immune systems can fight off. As the virus
destroys and impairs the function of immune cells, infected individuals
gradually become immunodeficient. Immune function is typically measured by CD4
cell count.
The most advanced stage of HIV infection is acquired
immunodeficiency syndrome (AIDS), which can take many years to develop if not
treated, depending on the individual. AIDS is defined by the development of
certain cancers, infections or other severe long-term clinical manifestations.
Signs and symptoms
The symptoms of HIV vary depending on the stage of infection.
Though people living with HIV tend to be most infectious in the first few
months after being infected, many are unaware of their status until the later
stages. In the first few weeks after initial infection people may experience no
symptoms or an influenza-like illness including fever, headache, rash or sore
throat.
As the infection progressively weakens the immune system,
they can develop other signs and symptoms, such as swollen lymph nodes, weight
loss, fever, diarrhoea and cough. Without treatment, they could also develop
severe illnesses such as tuberculosis (TB), cryptococcal meningitis, severe
bacterial infections, and cancers such as lymphomas and Kaposi's sarcoma.
Transmission
HIV can be transmitted via the exchange of a variety of body
fluids from infected people, such as blood, breast milk, semen and vaginal
secretions. HIV can also be transmitted from a mother to her child during
pregnancy and delivery. Individuals cannot become infected through ordinary
day-to-day contact such as kissing, hugging, shaking hands, or sharing personal
objects, food or water.
It is important to note that people with HIV who are taking
ART and are virally suppressed do not transmit HIV to their sexual
partners. Early access to ART and support to remain on treatment is
therefore critical not only to improve the health of people with HIV but also
to prevent HIV transmission.
Risk factors
Behaviours and conditions that put individuals at greater
risk of contracting HIV include:
- having
unprotected anal or vaginal sex;
- having
another sexually transmitted infection (STI) such as syphilis, herpes,
chlamydia, gonorrhoea and bacterial vaginosis;
- sharing
contaminated needles, syringes and other injecting equipment and drug
solutions when injecting drugs;
- receiving
unsafe injections, blood transfusions and tissue transplantation, and
medical procedures that involve unsterile cutting or piercing; and
- experiencing
accidental needle stick injuries, including among health workers
Diagnosis
HIV can be diagnosed through rapid diagnostic tests that
provide same-day results. This greatly facilitates early diagnosis and linkage
with treatment and care. People can also use HIV self-tests to test themselves.
However, no single test can provide a full HIV diagnosis; confirmatory testing
is required, conducted by a qualified and trained health or community worker at
a community centre or clinic. HIV infection can be detected with great accuracy
using WHO prequalified tests within a nationally approved testing strategy.
Most widely-used HIV diagnostic tests detect antibodies
produced by the person as part of their immune response to fight HIV. In most
cases, people develop antibodies to HIV within 28 days of infection. During
this time, people experience the so-called window period – when HIV antibodies
haven’t been produced in high enough levels to be detected by standard tests
and when they may have had no signs of HIV infection, but also when they may
transmit HIV to others. After infection, an individual may transmit HIV
transmission to a sexual or drug-sharing partner or for pregnant women to their
infant during pregnancy or the breastfeeding period.
Following a positive diagnosis, people should be retested
before they are enrolled in treatment and care to rule out any potential
testing or reporting error. Notably, once a person diagnosed with HIV and has
started treatment they should not be retested.
While testing for adolescents and adults has been made
simple and efficient, this is not the case for babies born to HIV-positive
mothers. For children less than 18 months of age, serological testing is
not sufficient to identify HIV infection – virological testing must be provided
as early as birth or at 6 weeks of age. New technologies are now becoming
available to perform this test at the point of care and enable same-day
results, which will accelerate appropriate linkage with treatment and care.
Prevention
Individuals can reduce the risk of HIV infection by limiting
exposure to risk factors. Key approaches for HIV prevention, which are often
used in combination, include:
- male
and female condom use;
- testing
and counselling for HIV and STIs;
- testing
and counselling for linkages to tuberculosis (TB) care;
- voluntary
medical male circumcision (VMMC);
- use of
antiretroviral drugs (ARVs) for prevention;
- harm
reduction for people who inject and use drugs; and
- elimination
of mother-to-child transmission (MTCT) of HIV.
Treatment
HIV disease can be managed by treatment regimens composed of
a combination of three or more antiretroviral (ARV) drugs. Current
antiretroviral therapy (ART) does not cure HIV infection but
highly suppresses viral replication within a person's body and allows an
individual's immune system recovery to strengthen and regain the capacity to
fight off opportunistic infections and some cancers.
Since 2016, WHO has recommended that all people living with
HIV be provided with lifelong ART, including children, adolescents, adults and
pregnant and breastfeeding women, regardless of clinical status or CD4 cell
count.
By June 2021, 187 countries had already adopted this
recommendation, covering 99% of all people living with HIV globally. In
addition to the treat all strategy, WHO recommends a rapid ART initiation to
all people living with HIV, including offering ART on the same day as diagnosis
among those who are ready to start treatment. By June 2021, 82 low- and
middle-income countries reported that they have adopted this policy, and
approximately half of them reported country-wide implementation.
Globally, 28.2 million people living with HIV
were receiving ART in 2021. The global ART coverage rate was 73% [56–88%] in
2020. However, more efforts are needed to scale up treatment, particularly for
children and adolescents. Only 54% [37–69%] of children (0–14 years old) were
receiving ART at the end of 2020.