Mary D. Nettleman, MD, MS, MACP is the Chair of the Department of Medicine at Michigan State University. She is a graduate of Vanderbilt Medical School, and completed her residency in Internal Medicine and a fellowship in Infectious Diseases at Indiana University.
Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.
HIV is transmitted when infected material such
as blood or semen or other infected fluids gains access to a new host. In the
United States, surveillance statistics show there are approximately 1.1 million
people living with HIV infection, but 18% are unaware that they are infected.
Approximately 50,000 people get infected with HIV each year. Although the
epidemic first was recognized in homosexual men, it has spread broadly
throughout the U.S. New infections affect people from all subpopulations,
although some groups are more likely to be affected than others. Of the 47,500
new infections in 2010, 63% were in men who had sex with men (MSN), 25% were
acquired through heterosexual contact, and 8% were from injection drug use. HIV
infection has hit the African-American community harder than other groups, with
44% of new infections occurring in this population, compared to 31% in whites
and 21% in Hispanics. Over 600,000 Americans have died of HIV infection since
the epidemic began.
Worldwide, there are approximately 34 million people living with HIV, and
there are 2.5 million new cases each year. Since HIV infection was recognized,
there have been 30 million deaths as a result of HIV infection.
What are the different stages of an HIV infection?
Untreated infection with
HIV progresses over time and gradually impairs specific parts of the immune
system, especially by destroying the white blood cells known as CD4 lymphocyte
cells. This progression is described as occurring in stages. All stages require
laboratory confirmation of HIV infection.
There are multiple different staging
systems. For example, the Centers for Disease Control and Prevention case
definition uses a staging system based on how much damage has been done to the
Stage 1 disease is the earliest phase. Stage 1 has no unusual
infections or cancers or other conditions that would be associated with AIDS. In
other words, stage 1 disease has no "AIDS-defining conditions" (see below).
Although blood tests are positive for HIV, the CD4 cell count is at least 500
cells per microliter of blood (or >29% of all lymphocytes).
Stage 2 disease
occurs when the CD4 count is between 200-499 cells per microliter (14%-28% of
all lymphocytes), but again there are no AIDS-defining conditions present.
3 disease is synonymous with AIDS and is the most severe stage. There are two
ways of diagnosing stage 3 disease: either by CD4 counts below 200 cells per microliter (<14% of lymphocytes) or through documentation of an AIDS-defining
Another way to conceptualize HIV is according to the characteristics or
clinical manifestations: acute infection, clinical latency, or AIDS.
infection: Two to four weeks after infection with HIV, the patient can experience an
acute illness, often described as "the worst flu ever." This is called acute
retroviral syndrome (ARS) or primary HIV infection, and it is caused by the
body's natural response to the HIV infection. Not all newly infected people
develop ARS, however -- and it can take up to three months for it to appear. During
this period of infection, large amounts of virus are being produced. The virus
uses CD4 cells to replicate and destroys them in the process. Because of this,
the CD4 count can fall rapidly. Eventually, the immune response will begin to
bring the level of virus in the body back down to a level called a "viral set
point," which is a relatively stable level of virus in the body. At this point,
the CD4 count begins to increase, but it may not return to pre-infection levels.
The human immune response suppresses the virus but does not eliminate it from
Clinical latency: After the acute stage of HIV infection, the
disease moves into a stage called clinical latency. This period is sometimes
called asymptomatic HIV infection or chronic HIV infection. During this phase,
HIV reproduces at very low levels, although it is still active. In this state,
infected people may be able to maintain an undetectable viral load and a healthy
CD4 cell count without the use of medication for a time. There are usually few
if any symptoms. This period can last up to eight years or longer. However, some
people progress through this phase faster than others. It is important to
remember that people are still able to transmit HIV to others during this phase.
Toward the middle and end of this period, the viral load begins to rise and the
CD4 cell count begins to drop. As this happens, infected people may begin to
have constitutional symptoms such as fatigue and other nonspecific symptoms.
AIDS: As the number of CD4 cells falls below 200 cells per cubic millimeter of
blood (200 cells/cubic milliliter), people will be diagnosed as having AIDS.
Normal CD4 counts are between 500 and 1,600 cells per cubic milliliter. This is
the stage of infection that occurs when the immune system is badly damaged and
patients become vulnerable to opportunistic infections. Without treatment,
people who are diagnosed with AIDS typically survive about three years. Once someone
has a dangerous opportunistic infection, life expectancy falls to about one year.
AIDS-defining conditions in an HIV-infected person include the following:
bronchi, trachea, lungs, or esophagus