Why does a common cold become life-threatening for some individuals? The answer lies in how specific pathogens attack the body's primary defense mechanisms. HIV is a virus that specifically targets and destroys the immune system. Unlike many other viruses, it does not infect general body cells; instead, it specifically attacks a type of white blood cell called a lymphocyte (often referred to as T-helper cells).
The destruction of these cells happens in a distinct, step-by-step process:
It can take years for a viral infection to reveal its most devastating effects. As HIV continues to replicate, the number of lymphocytes in the patient's blood drops significantly. Because lymphocytes are responsible for producing antibodies, their destruction means the immune system can no longer mount an effective response against everyday pathogens.
This continuous weakening of the immune system eventually leads to AIDS, the final and most severe clinical stage of an HIV infection. A patient is considered to have AIDS when their immune system is so degraded that they become highly susceptible to an opportunistic infection—such as tuberculosis or pneumonia—which a healthy body would easily defeat. While antiretroviral drugs can effectively pause viral replication and manage the condition, they do not provide a cure.
A standard flu might make your joints ache, but certain pathogens physically break open your blood vessels from the inside. is a severe disease caused by the Ebola virus. In stark contrast to HIV, the Ebola virus invades and destroys general body cells.
An infection initially presents with flu-like symptoms, including a high temperature, headaches, and muscle pain, before escalating to rashes, vomiting, and diarrhoea. The defining characteristic of the disease is haemorrhagic fever. This severe clinical condition involves a dangerously high fever paired with internal bleeding. The bleeding occurs because the rapidly replicating virus causes the body's capillaries and internal organs to rupture (lyse) from the inside out.
Stopping a deadly outbreak requires understanding exactly how the pathogen moves from person to person. Both HIV and Ebola are transmitted through direct contact with infected bodily fluids, but their transmission profiles differ.
HIV is primarily categorised as a Sexually Transmitted Infection (STI) and is passed through fluids such as blood, semen, vaginal fluids, and breast milk. Ebola spreads through an even broader range of fluids, including saliva, mucus, vomit, and faeces. Furthermore, Ebola can spread through secondary transmission via contaminated surfaces or items (fomites), such as infected bedding.
To prevent the spread of Ebola during an outbreak, three primary measures must be taken:
| Feature | HIV | Ebola |
|---|---|---|
| Target Cells | Specific immune cells (lymphocytes) | General body cells |
| Primary Symptom / Result | Weakened immune system leading to AIDS | Haemorrhagic fever (internal bleeding) |
| Transmission Route | Bodily fluids (mainly as an STI) | Bodily fluids and contaminated surfaces |
| Treatment / Control | Antiretroviral drugs to halt replication | Isolation, sterilisation, and strict hygiene/PPE |
Students often write 'HIV virus' in the exam. This is redundant as the 'V' already stands for Virus. Simply write 'HIV'.
For Higher Tier questions, explicitly state that HIV targets 'lymphocytes' or 'T-helper cells'. Avoid using the generic term 'white blood cells' to secure maximum marks.
If a question asks you to compare Ebola and HIV, always highlight their distinct cellular targets: HIV destroys immune cells, whereas Ebola targets general body cells.
When explaining how HIV leads to death, examiners specifically look for the phrase 'increased susceptibility to opportunistic infections' rather than just saying 'the immune system stops working'.
HIV
The Human Immunodeficiency Virus; a pathogen that attacks and destroys lymphocytes, leading to a weakened immune system.
Lymphocyte
A specific type of white blood cell that produces antibodies and coordinates the immune response; it is the primary target of HIV.
Bodily fluids
Any liquid originating from inside the human body (such as blood, semen, or saliva) which can act as a medium for transmitting pathogens.
Antibodies
Proteins produced by lymphocytes that bind to specific antigens on pathogens to help destroy them.
AIDS
Acquired Immune Deficiency Syndrome; the final clinical stage of an HIV infection where the immune system is entirely compromised.
Opportunistic infection
An illness caused by a pathogen that takes advantage of a host with a weakened immune system, commonly seen in AIDS patients.
Ebola
A highly infectious disease caused by a virus that targets general body cells, leading to severe internal bleeding and fever.
Haemorrhagic fever
A severe clinical condition characterised by a high temperature and internal or external bleeding due to damaged blood vessels.
Isolation
The practice of physically separating infected individuals from the healthy population to prevent the spread of an infectious disease.
Sterilisation
The process of completely destroying all microbial life on surfaces or equipment to prevent secondary transmission of diseases like Ebola.
Put your knowledge into practice — try past paper questions for Biology
HIV
The Human Immunodeficiency Virus; a pathogen that attacks and destroys lymphocytes, leading to a weakened immune system.
Lymphocyte
A specific type of white blood cell that produces antibodies and coordinates the immune response; it is the primary target of HIV.
Bodily fluids
Any liquid originating from inside the human body (such as blood, semen, or saliva) which can act as a medium for transmitting pathogens.
Antibodies
Proteins produced by lymphocytes that bind to specific antigens on pathogens to help destroy them.
AIDS
Acquired Immune Deficiency Syndrome; the final clinical stage of an HIV infection where the immune system is entirely compromised.
Opportunistic infection
An illness caused by a pathogen that takes advantage of a host with a weakened immune system, commonly seen in AIDS patients.
Ebola
A highly infectious disease caused by a virus that targets general body cells, leading to severe internal bleeding and fever.
Haemorrhagic fever
A severe clinical condition characterised by a high temperature and internal or external bleeding due to damaged blood vessels.
Isolation
The practice of physically separating infected individuals from the healthy population to prevent the spread of an infectious disease.
Sterilisation
The process of completely destroying all microbial life on surfaces or equipment to prevent secondary transmission of diseases like Ebola.