Flashcards in HIV/AIDS and TB (Chapter 10) Deck (37)
What does AIDS stand for?
Acquired Immune Deficiency Syndrome
What is the pathogen of AIDS?
HIV (Human Immunodeficiency Virus)
What are the three methods of transmission of HIV?
1) sexual intercourse through semen and vaginal fluids
2) transmission of infected blood (e.g. through blood donation and the sharing of needles used by intravenous drug users)
3) mother to foetus across the placenta and through mixing of blood during birth
What are the sites of action of HIV?
T helper lymphocytes, macrophages, brain cells
What are the symptoms of HIV and AIDS?
HIV - flu-like symptoms then symptomless
AIDS - opportunistic infections (e.g. TB, Karposi's sarcoma, pneumonia, malaria) and weight loss, diarrhoea
What kind of virus is HIV?
A retrovirus - it has RNA not DNA
What happens when HIV infects?
1) once inside a host cell, the viral RNA is converted to DNA to be incorporated into human chromosomes
2) the virus infects and destroys cells of the body's immune system (helper T cells) so that their numbers gradually decrease
3) when the numbers of cells are low, the body is unable to defend itself against infection, ∴ allowing a rang of pathogens to cause a variety of opportunistic infections
What is AIDS?
A collection of opportunistic disease associated with immunodeficiency cause by a HIV infection
What is the only way that transmission of HIV is possible?
Through direct exchange of bodily fluids
How can HIV spread more easily?
Having multiple sex partners
Why may someone not have any symptoms of HIV until years later?
HIV is a slow virus
When is a person HIV+?
When they appear not to develop any initial symptoms except flu-like symptoms for several weeks after becoming infected
What is the difference between AIDS in developed and developing countries?
Most likely causes of death of people with AIDS:
Developed countries - cancers of internal organs, dementia
Developing countries: malnutrition, malaria and TB
Why does AIDS have an adverse effect on the economic development of countries?
1) it affects sexually active people in their 20s and 30s who are the most economically productive
2) the purchase of expensive drugs drains government funds
How is HIV/AIDS treated?
- There is no cure for AIDS and no vaccine for HIV
- Drug therapy can slow down the onset of AIDS significantly e.g. zidovudine which binds to the viral enzyme reverse transcriptase and blocks its action - but drugs are expensive and have side effects
- Combination drug therapy
Why is the spread of HIV/AIDS difficult to control?
1) the virus has a long latent stage ∴ it can be transmitted by people who are HIV+ but show no symptoms of AIDS and do not know that they are infected
2) the virus changes its surface proteins, making it difficult for the body's immune system to recognise it and to make a vaccine
How do public health measures steps the spread of HIV/AIDS?
1) people can be educated about the spread of infection and encouraged to change behaviour to protect themselves and others
2) condoms, femidoms and dental dams reduce risk of infection during intercourse, forming a barrier between body and fluids, reducing chance of transmission
What is contact tracing?
- If a person who is diagnosed as HIV+ and identifies the people who they have put at risk of infection by sexual intercourse or needle sharing, then these people will be offered a HIV test
- This test identifies the presence of antibodies to HIV
How can the spread of HIV be prevented?
1) injecting drug users are advised to give up on their habit, stop sharing needles, or take their drug another way - needle exchange schemes also exist to exchange used needles for sterile ones
2) blood collected from blood donors is screened for HIV and heat-treated to kill any viruses and people who think they might have been infected are encouraged not to donate
3) HIV-testing is promoted most strongly to high-risk groups e.g. male homosexuals, prostitutes and injecting drug users
4) mother to child transmission is reduced by treating HIV+ women and their babies with drugs mothers are encouraged not to breastfeed their babies
What are the two pathogens of TB?
Myobacterium tuberculosis and Myobacterium bovis
What is are the methods of transmission of TB?
M. tuberculosis: airborne droplets
M. bovis: undercooked meat and unpasteurised milk
What are the symptoms of TB?
Racking cough, coughing blood, chest pain, fever
What is special about TB?
- Some people become infected with and develop TB quite quickly, while in others the bacteria can remain inactive for many years
- People with the inactive infection do not spread the disease
What is the relationship between TB and HIV?
- TB is often the first opportunistic infection to strike HIV+ people
- HIV infection may reactivate dormant infection of M. tuberculosis or make then susceptible to infection
When are TB bacteria most likely to become active?
When people are weakened by other diseases e.g. malnutrition or infected with HIV
How is TB spread?
1) infected people with the active form of the illness caught or sneeze and TB is carried in the air in tiny droplets of liquid
2) uninfected people then inhale the liquid
How is TB spread most rapidly?
Among people living or sleeping in overcrowded conditions - ∴ mainly attacks those in poor housing or the homeless
Why did TB incidence decrease steeply?
1) improvements in housing conditions and diet
2) antibiotic streptomycin introduced in 1940s
3) vaccine introduced in 1950
Why is TB on the increase?
1) some strains of TB bacteria being resistant to drugs
2) HIV/AIDS pandemic
3) poor inner city housing and homelessness
4) breakdown of TB control programmes - partial treatment for TB increase the chance of drug resistance