Lesson 1 of 5 / Infection, vaccination and disease spread
How viruses disrupt host function
Why do influenza and HIV damage different systems?
I can explain influenza epithelial damage and HIV helper T-cell impairment.
I can explain influenza and HIV disease through effects on host cells and tissues.Syllabus
Syllabus 9477, Extension A(g). Explain influenza and HIV disease through effects on host cells and tissues.
About 7 min
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Each virus binds receptors on different cells.
Influenza binds receptors on respiratory epithelium; HIV binds receptors on helper T cells. Tropism follows receptors.
The key idea
Viral tissue tropism links receptor recognition and replication to the host functions that are disrupted.
Connect cause and consequence
Why do different target cells produce different effects?
Cilia and mucus help remove inhaled material. Cell targeting explains how injury here affects respiratory defence.
Original tissue/cell comparison; dimensions and cell counts are illustrative. The controls show a mechanism, not a forecast of disease progression in any person.
Explanation
Influenza infects susceptible respiratory epithelial cells. Viral replication and immune responses can damage or remove these cells, impairing the protective respiratory surface and mucociliary clearance. The effects follow from damage to a tissue that normally forms a barrier and removes inhaled material.
HIV infects cells with suitable receptors and co-receptors, including helper T cells. Persistent infection can reduce their number and function, weakening coordination of adaptive immune responses. This increases vulnerability to opportunistic infections and some cancers as immune protection declines.
A viral genome does not damage all tissues identically. Receptor distribution, intracellular compatibility and host responses shape which cells support infection and what functions are lost. The immune response can control infection while also contributing to inflammation and tissue injury.
Distinguish the agent from the syndrome: HIV is a virus, while AIDS describes an advanced immune-deficiency syndrome associated with HIV infection. These mechanistic distinctions support syllabus reasoning and should not be used as a diagnosis from symptoms alone.
Step by step
- 1
Name the target cell
Avoid saying simply that the virus attacks the body.
- 2
Explain disruption
Connect replication or immune injury to cell loss/function.
- 3
State the system-level consequence
Barrier impairment or weakened immune coordination.
Worked example
Work through the evidence
Why can HIV increase susceptibility to pathogens unrelated to HIV itself?
One way to explain it
Loss of helper T-cell coordination weakens several adaptive immune pathways, so control of other pathogens becomes less effective.
Why this answer works
- The effect is on the defence system, not a need for the new pathogen to be a retrovirus.
- Different infections can exploit the same immune deficit.
Watch out for this
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HIV is the virus; AIDS is a syndrome of advanced immune deficiency.
Check your understanding
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Respiratory epithelial damage can impair mucociliary defence.
Damage to those cells reduces an important protective function.
Quick recall
Why do influenza and HIV damage different systems?