HIV Overview and Case Definitions

A unique retrovirus that causes progressive immune system dysfunction, leading to susceptibility to opportunistic infections and malignancies.

The initial phase of HIV infection, often presenting with flu-like symptoms 2-6 weeks after exposure.

The period following acute HIV infection where individuals may experience no symptoms or only mild symptoms.

A type of immune cell that helps the body fight infections. HIV specifically attacks these cells.

A measure of the number of CD4 cells per cubic millimeter of blood, used to assess the severity of HIV infection.

The stage of HIV infection when the immune system is severely weakened, making individuals highly susceptible to opportunistic infections and malignancies.

A high level of HIV in the blood, increasing the risk of transmission to others.

Inflammation of the meninges, the membranes surrounding the brain and spinal cord. It can be a symptom of acute HIV infection.

A type of immune response to HIV infection where the number of CD4 cells decreases significantly.

A decrease in the number of platelets in the blood, potentially contributing to increased bleeding.

The presence of other sexually transmitted infections (STIs) like syphilis, gonorrhea, or herpes simplex type 2 significantly increases the risk of HIV transmission.

HIV can be transmitted from mother to child during pregnancy, childbirth, or breastfeeding.

The risk of HIV transmission through contaminated needles is high among individuals who inject illicit drugs.

High levels of HIV in the blood (viral load) increase the risk of transmission to others.

Treatment success is defined as a sustained decline in viral load (VL) to below 50 copies/mL within 6 months of starting ART, and maintained thereafter.

A protein on the surface of immune cells, primarily macrophages and T lymphocytes, that HIV binds to as its primary receptor.

A second type of receptor, besides CD4, that HIV needs to bind to in order to enter the cell.

Chemokine receptors that act as coreceptors for HIV entry, such as CCR5 and CXCR4.

A specific HIV coreceptor that is primarily used by macrophage-tropic strains of HIV-1.

A specific HIV coreceptor that is mainly used by lymphocyte-tropic strains of HIV-1.

The process of the HIV virion attaching to CD4 and then the coreceptor, with the virus's envelope proteins undergoing conformational changes.

The gene in HIV that encodes for the envelope glycoproteins gp120 and gp41.

An enzyme present within the HIV virion that converts the viral RNA into DNA, a crucial step in the HIV replication cycle.

The process of HIV's genetic material (DNA) becoming integrated into the host cell's DNA, allowing the virus to lie dormant or become active later.

The enzyme that catalyzes the integration of the linear HIV DNA into the host's DNA.

HIV is a spherical virus with a cylindrical core. Its genetic material is RNA, which is single-stranded, linear, and positive-sense. It has a diploid genome (meaning two copies of its RNA).

The gag gene codes for structural proteins like the matrix, capsid, and nucleocapsid, which form the core of the virus. The pol gene encodes for enzymes like protease, reverse transcriptase, and integrase, essential for viral replication. The env gene produces envelope glycoproteins, which help the virus attach to and enter host cells.

The prevalence of HIV, which measures the percentage of people with the virus in a population, is highest in sub-Saharan Africa. This region is home to more than two-thirds of the world's people living with the virus.

HIV-1 is responsible for most HIV infections worldwide, while HIV-2 is mostly found in West Africa. It's thought to be less virulent (less likely to cause disease rapidly).

HIV infection progresses through distinct stages: Acute Retroviral Syndrome, Asymptomatic Stage, and AIDS. Each stage has characteristic symptoms and immune system status.

HIV primarily targets CD4+ T cells, a type of white blood cell crucial for immune function. As the virus destroys CD4+ cells, the immune system becomes progressively weakened.

The CD4 count, or number of CD4+ cells per cubic millimeter of blood, is a key marker used to monitor the severity of HIV infection. A declining CD4 count indicates weakened immunity and progression towards AIDS.

Opportunistic infections often occur in people with weakened immune systems due to HIV infection. These infections are caused by organisms that wouldn't usually cause harm in a healthy individual.

The integrated form of the HIV virus's genetic material within a host cell's DNA.

The chronic phase of HIV infection, where the virus is dormant, and there are no or very few symptoms.

The state where HIV is actively replicating, causing gradual immune system decline.

The final stage of HIV infection, marked by a rapid decline in immune function and severe opportunistic infections.

The cells and tissues where HIV can reside and persist in the body, even when antiviral therapy is effective.

The first line of defense against HIV infection, involving cells like macrophages and NK cells.

Proteins that recognize specific structures on pathogens, triggering immune responses.

A type of immune cell that displays antigens from pathogens to initiate an adaptive immune response.

Specialized immune cells responsible for targeting and destroying specific pathogens.

The transition from the innate to adaptive immune response, allowing the immune system to recognize and fight specific pathogens efficiently.

HIV-specific CD8+ T cells kill infected cells, preventing viral spread in blood.

These immune cells produce IFN-γ to create an antiviral environment and chemokines that hinder HIV's ability to infect new cells.

Mutations in HIV allow it to escape recognition by the immune system, ultimately leading to continued viral replication.

B cells create neutralizing antibodies after initial viral decline, but their effectiveness is limited due to the high variation in HIV's protein coat.

The presence of sugars on the surface of HIV interferes with the ability of antibodies to bind and neutralize it.

HIV can evade neutralizing antibodies by rapidly changing its protein coat, rendering existing antibodies useless.

CD4+ T cells, vital for immune function, are targeted and destroyed by HIV, weakening the immune system.

HIV infects and depletes CD4+ T cells, leading to a weakened immune system and susceptibility to infections.

Despite vigorous immune responses, HIV persists in the body due to its ability to spread directly between cells, evade immune recognition, and mutate rapidly, leading to immune escape.

HIV's ability to integrate its DNA into the host's genome allows it to persist indefinitely, making eradication challenging.