infectious diseases

• Disease: ill-health or sickness causes reduced effectiveness of functions, has a set of symptoms, can be poor physical, mental, social well-being
• Infectious diseases: transmissible diseases caused by a pathogen which causes a reduced effectiveness of function
• vibrio cholerae is the pathogen that causes cholera and is a bacteria
• cholera is transmitted through the faecal-oral route
• how does the pathogen work?

  Bacteria secretes choleragen toxin which binds to complementary receptor on intestinal cells via endocytosis, loss of Na+ and Cl- from cells, water moves out of blood
• what are the symptoms of cholera?

  Severe diarrhoea, severe dehydration, loss of water and salts, fatigue
• how do you treat cholera?

  through oral-rehydration therapy
• how is cholera prevented?

  Proper sewage treatment, chlorinate water, drink bottled waters, no effective vaccine due to mutation and several strains
• global distribution: Outbreaks follow natural disasters due to lack of proper sanitation, poor hygiene and living conditions.
• what pathogens cause malaria?

  Plasmodium falciparum Plasmodium vivax Plasmodium ovale Plasmodium malariae
• what type of pathogen causes malaria?

  protocist
• how is malaria transmitted?

  vector female anapholes mosquito where the mosquito takes a blood meal and the parasite enters the host
• where does the pathogen act?

  in the RBCs, liver and brain
• method of action: Parasite enters blood stream and matures in liver cells, enters RBCs, divide in RBCs causing it to lyse, infect other RBCs
• what are the symptoms of malaria?

  fever, anameia and enlarged spleen
• how is malaria diagnosed?

  dipstick test, microscopical analysis of blood
• how is malaria treated?

  through prophylactic antimalarial drugs; artemisinin-based combination therapy (ACT)
• how is malaria prevented?

  Use preventative drugs, Reduce no. of mosquito:Spray insecticides, Spread oil over water surface to prevent breeding, Breeding fish that feed on larvae, Spray Bacillus thuringiensis bacteria to kill larvae.
• how are bites from vector mosquito anapheles mosquitoes prevented?

  Use mosquito nets soaked in insecticides or Repellents and there is No vaccination available
• global distribution: Endemic in tropical and sub-tropical areas: - vector breeds in hot and humid and needs stagnant water to reproduce - Plasmodium reproduce within mosquito at >20C
• Drug resistant Plasmodium, insecticide DDT resistant mosquito, difficulty developing vaccine, migration
• what pathogen causes HIV/AIDS?


  Human Immunodeficiency Virus (HIV)
• what type of pathogen causes HIV/AIDS?

  virus (RNA retrovirus)
• how is HIV/AIDS transmitted?

  Direct exchange of bodily fluids through semen/vaginal fluids during sexual intercourse, blood tranfusions, mother-to-baby across placenta/breast milk
• where does the HIV virus act?

  in the T-helper lymphocytes
• what is the HIV virus' method of action?

  Slow infection. Viral RNA and reverse transcriptase (RT) enters T-helper cells, coverts RNA → DNA, viral DNA incorporated into host DNA, cell expresses viral proteins, T-helper cells cannot function
• what are the symptoms of HIV?

  AIDS and opportunistic infections ex: TB, malaria, oral thrush or cancers
• how is HIV/AIDS diagnosed?

  blood/ saliva or urine test
• how is HIV treated?

  there is no vaccination and no cute but there are drugs to slow down the onset of AIDS: Zidovudine inhibits RT and viral enzymes. also combination therapy
• how is HIV/AIDS prevented?

  Use condoms, femidoms, dental dams. Provide HIV testing centres and contact tracing Control mother child transmission using drugs. High income HIV+ women should avoid breastfeeding to reduce transmission. Low income HIV+ women should breastfeed for passive immunity
• Pathogen

  • Mycobacterium tuberculosis
  • Mycobacterium bovis
• Type of pathogen

  • Bacteria
• Transmission of M. tuberculosis

  Infected person sneezes and the airborne droplets are breathed in by the uninfected person
• Transmission of M. bovis

  From infected cattle e.g. unpasteurized milk
• Method of action

  • Slow infection. Disease can stay dormant and become active later when immune system weakened e.g. by HIV
• Treatment

  Combination therapy of several antibiotics to prevent resistance. Through DOTS (direct observation treatment, short course)
• Prevention


  • BCG vaccine
  • Contact tracing
  • Quarantine
  • Pasteurise milk
• Global Distribution


  • Endemic due to high rate of migration, HIV/AIDS prevalence, overcrowded living spaces
• Other Problems

  • MDR-TB and XDR-TB, requires longer treatment with more expensive antibiotics
• Antibiotics

  Drug that kills or stops the growth of bacteria, without harming the cells of the infected organism