HIV/AIDS, TB, & Malaria (The 3 Big Killers)/NTD

HIV

• A virus that attacks CD4 T cells (immune system cells).

• A retrovirus (RNA → DNA using reverse transcriptase).

• Can be managed with treatment.(virus)

AIDs

• The advanced stage of untreated HIV infection.

• Diagnosed when:

  • CD4 count drops very low, OR

  • Certain opportunistic infections develop.

  • late-stage condition caused by untreated HIV

modes of transportation of HIV- Blood-to-blood

• Sharing needles

• Blood transfusions (rare today with screening)

modes of transportation of HIV- sexual contact

• Higher risk:

  • Unprotected anal sex

  • Unprotected vaginal sex

• Lower risk:

  • Oral sex (much lower risk)

mother-to-child transmission

• During pregnancy

• During childbirth

• Through breastfeeding

What contributes to higher rates of transmission of HIV

• Other STIs (increase susceptibility)

• High viral load (acute and late-stage infection)

• Lack of condom use

• Needle sharing

• Limited access to healthcare

What helps lessen these rates?

• Health education 

• condom use

• U=U → If viral load is undetectable, sexual transmission does not occur.

• PrEP (Pre-exposure prophylaxis) – medication taken before exposure

• PMTCT (Prevention of Mother-To-Child Transmission)

 Have a general understanding of the life cycle of HIV

• Attachment & Fusion

  • gp120 binds to CD4 receptor + CCR5/CXCR4 co-receptor

  • gp41 allows fusion

• Reverse Transcription

  • Viral RNA → DNA

• Integration

  • Viral DNA inserts into host DNA

• Transcription

  • Host cell makes viral RNA

• Translation

  • Viral proteins made

• Assembly & Budding

  • New viruses form and leave the cell

What is the most common opportunistic infection associated with HIV in resource-limited settings?

• The most common opportunistic infection is Tuberculosis (TB), caused by Tuberculosis.

  • Leading cause of death for people with HIV globally

Think about social aspects influencing the health outcomes of those with HIV.

• Poverty

• Stigma and discrimination

• Limited healthcare access

• Gender inequality

• Education level

• Political instability

Active TB. 

• Symptoms (cough, fever, weight loss)

• Contagious (airborne spread)

• Can be fatal if untreated

latent TB

• Bacteria present

• No symptoms

• Not contagious

When someone has both HIV and TB:

• HIV weakens immune system

• Latent TB becomes active more easily

• TB progresses faster

• Higher mortality risk

Implications of TB

• Major global health burden

• Strains healthcare systems

• Requires integrated HIV/TB treatment programs

What is the parasite? What is the vector?

• Caused by the parasite Plasmodium.

• Vector: The female Anopheles mosquito transmits malaria through bites.

life cycle of malaria

1. Mosquito bites → injects parasites into bloodstream

2. Parasites infect liver cells

3. Multiply and enter red blood cells

4. Red blood cells burst → symptoms (fever cycles)

5. Mosquito bites infected person → cycle continues

What environmental factors contribute to the higher prevalence of malaria in certain regions?

• Warm temperatures

• High rainfall

• Standing water

• Poor drainage

• Weak housing infrastructure

• Climate change is expanding mosquito habitats

epidemiological triangle

• Agent – Plasmodium parasite

• Host – Humans (immunity level matters)

• Environment – Warm climate, mosquitoes present

target the vector (based on the triangle)

• Insecticide-treated bed nets

• Indoor residual spraying

• Eliminate standing water

protect the host (based on the triangle)

• Preventive medications

• Vaccination (in some regions)

• Protective clothing

reduce the agent (based on the triangle)

• Early diagnosis

• Effective treatment

Neglected tropical diseases

are a group of diseases that primarily affect over 1 billion people worldwide, with 1.5 billion requiring treatment annually and ~200,000 deaths preventable each year.

why are NTDs called neglected

because they have low visibility, limited political attention, and resources are focused on HIV/AIDS, TB, malaria, and COVID-19.

Underlying factors contributing to NTDs:

• Unsafe drinking water

• Poor sanitation

• Inadequate housing

• Poverty and limited access to healthcare

Climate change affects vector-borne NTDs by altering:

• Temperature → influences vector survival, feeding behavior, pathogen development

• Precipitation → can increase or decrease breeding sites

• Geographic spread → potential outbreaks in new areas where populations lack immunity