Infectious Disease: Cambridge AS-A Level PDF

Ver. 2024/2025 Infectious Disease Grade 11 Cambridge AS-A Level Teacher: Deera A. Pramana Slide guide warmer keep yourself curious & interested, relate to real world cases retrieving recall the relevant basic prior conce...

Ver. 2024/2025 Infectious Disease Grade 11 Cambridge AS-A Level Teacher: Deera A. Pramana Slide guide warmer keep yourself curious & interested, relate to real world cases retrieving recall the relevant basic prior concepts. It helps you understand better. target the main concepts you need to comprehend enrichment additional concepts to prepare for AS/A-level exam or bio-related uni. program applying practical activities to nurture your kinaesthetic talent elaboration strengthen and broaden your knowledge even more affective develop and internalize emotion, beliefs and values warmer What is DISEASE? /dɪˈziːz/ Any experience worth sharing? warmer Throwback: COVID-19 pandemic What did you learn from this pandemic? https://data.who.int/dashboards/covid19/deaths warmer (some of) the past pandemic and plague events warmer Match the terms and their meaning! objective evidence of disease perceptible to the diagnosis examining practitioner disease signs subjective evidence of disease perceived by the patient the act or process of identifying or determining the disease symptoms nature and cause of a disease or injury through evaluation of patient history, examination of a patient, and review of laboratory data warmer Match the terms and their meaning! incubation period an organism that causes disease a time when something suddenly begins, especially a pathogen disease or something else dangerous or unpleasant outbreak an organism where the pathogen lives host the process or period of time in which pathogen increase in size or number in a person's or animal's body but do not yet produce the effects of disease Learning Objectives 10.1 Infectious diseases 10.1.1 State that infectious diseases are caused by pathogens and are transmissible. 10.1.2 State the name and type of pathogen that causes each of the following diseases: cholera malaria tuberculosis (TB) HIV/AIDS 10.1.3 Explain how cholera, malaria, TB and HIV are transmitted. 10.1.4 Discuss the biological, social and economic factors that need to be considered in the prevention and control of cholera, malaria, TB and HIV (details of the life cycle of the malarial parasite are not expected). target Infectious = transmissible = communicable = contagious target vocabulary disease transmission: the transfer of a pathogen incidence of a disease: the number of people from a person infected with that pathogen to an who are diagnosed (as new cases) over a certain uninfected person period of time, usually a week, month or year. transmission cycle: the passage of a pathogen prevalence of a disease: the number of people from one host to another is continually repeated who have that disease at any one time. as the pathogen infects new hosts disease eradication: the complete breakage of epidemic : sudden increase in the number of people the transmission cycle of a pathogen so that with a disease. there are no more cases of the disease caused pandemic: increase in the number of cases by the pathogen anywhere in the world throughout a continent or across the world. disease carrier (or simply carrier): person mortality rate: the number of deaths over a particular infected with a pathogen who shows no length of time (usually a year) symptoms, but can be the source of infection in other people (not carrier of an inherited disease) endemic disease: a disease that is always in a population elaboration The reservoir of an infectious agent is the habitat in which the agent normally lives, grows, and multiplies. Reservoirs include humans, animals, and the environment. The reservoir may or may not be the source from which an agent is transferred to a host. target /ˈpæθ.ə.dʒən/ Pathogen types & some example of infectious diseases ⭐ ⭐ ⭐ worms Cholera, Tuberculosis Mode of transmission Mechanical target vocabulary direct contact: spread through skin-to-skin contact, vehicle borne: indirect spread of infectious sexual activity, and also contact with soil or diseases through contaminated fomites vegetation harboring infectious organisms (inanimate objects such as handkerchiefs, droplet spread: spread by direct spray over a few bedding, or surgical scalpels) or shared feet with relatively large, short-range aerosols resources like food, water, air, or blood product produced by sneezing, coughing, or even talking waterborne: carried by or through water disease vector: an organism which carries a airborne: infectious agents are carried by dust pathogen from one person to another or from or droplet nuclei suspended in air (droplet nuclei an animal to a human are dried residue of less than 5 microns in size) biological vectors → carry pathogens that can multiply within their bodies and be delivered to new hosts, usually by biting. mechanical vectors → pick up infectious agents on the outside of their bodies and transmit them through physical contact. warmer Cholera The John Snow pub with a replica of the original water pump, at right, that in 1854 Dr John Snow tracked down as the drinking water source of a cholera outbreak that killed more than 500 people. target Cholera Incubation period: 2 hours - 5 days Pathogen: Vibrio cholerae (a bacteria) Site of action of the pathogen: wall of small intestine After cholera pathogens are ingested, if they survive the stomach acid, the bacteria will attach to the intestine wall. The bacteria multiply and secrete toxin, choleragen. Choleragen disrupts the functions of the epithelium lining the intestine, so that salts and water leave the blood (failed to be absorbed) → severe diarrhoea → loss of fluid → can be fatal if not treated within 24 hours target Methods of diagnosis: Cholera - dipstick test of rectal swabs; - identification of V. cholerae in faecal samples using Symptoms: microscopy dipstick test profuse watery diarrhoea, (rice-water stools) vomiting faecal swab thirst leg cramps restlessness or irritability diarrhoea (UK), diarrhea (US) /ˌdaɪəˈrɪə/ an illness in which your solid waste is more liquid than usual, and comes out of your body more often faecal sample target target Cholera Transmission: contaminated water & food (water-borne & food-borne) Global distribution: Asia, Africa, Latin America (especially places with poor sanitation) Annual incidence worldwide in 2017: 1.3 million to 4.0 million (WHO estimate) Annual mortality worldwide in 2017: 21,000 to 143,000 (WHO estimate) elaboration Health authorities always fear outbreaks of cholera and other diarrhoeal diseases following natural disasters or war. target Cholera Treatment: - Antibiotic → to kill the bacteria - rehydration (oral or intravenous) with salt and glucose solution → to maintain the osmotic balance of intravenous rehydration the blood and tissue fluids. → glucose absorption into the blood intravenous /ˌɪntrəˈviːnəs/ put directly into your veins is linked to the uptake of sodium and potassium ions → help rehydration /ˌriː.haɪˈdreɪ. maintain the osmotic pressure in ʃən/ the blood the process of putting water into someone's body when they are suffering from dehydration oral /ˈɔːrəl/ relating to or using the mouth target Cholera Prevention: Break the cycle of transmission! DOs build proper sanitation treat sewage & faeces to avoid contaminating clean water build facilities to supply clean water cook water and food properly wash hands before eating take oral vaccine for cholera DON’Ts use of raw human sewage to irrigate/ fertilise vegetables cook and wash in contaminated water warmer Be critical: read the caption and tell us what you think of it warmer Be critical: why is so it important for Indonesia to be free from malaria? target Malaria Pathogen: four species of Plasmodium Incubation period: 1 week - 1 year Plasmodium falciparum Plasmodium malariae Plasmodium ovale Plasmodium vivax → a type of protozoa, protoctist Site of action of the pathogen: liver, red blood cells, brain Plasmodium enter the bloodstream and then liver cell during its infective stage The pathogens multiply inside the red blood cells & destroy them when getting out → anaemia → can be fatal elaboration The life cycle of Plasmodium target Malaria Methods of diagnosis: - dipstick test for malaria antigens Symptoms: in blood Fever, shivering, sweating - microscopical examination of anaemia, blood dipstick test nausea, headaches, muscle pain, enlarged spleen blood sample → Doctors who see very few cases of malaria, often misdiagnose it as influenza, since the initial symptoms are similar. target Malaria anticoagulant: a drug or other substance that prevents or slows down the process of blood forming Transmission : a clot (= a solid mass) insect vector, female Anopheles mosquito (about 30 different species) → when biting, mosquito injects anticoagulant through its saliva to prevent blood clotting → the pathogens also flow out to the bloodstream. This transmission mode is affected by: - Lifespan & human-biting habit of the mosquito → differs in the mosquito species - Survival of the mosquito → depends on climatic conditions (rainfall patterns, temperature and humidity) through blood transfusion from mother to fetus through the placenta target Malaria Global distribution: throughout the tropics and sub-tropics (endemic in 106 countries) → mosquitos favor warm and humid climate → 40% of the world’s population lives in areas where there is a risk of malaria Annual incidence worldwide in 2017: 219 million cases of malaria – in 90 countries (WHO estimate) 92% of cases are in Africa Annual mortality worldwide in 2017: 435 000 deaths (WHO estimate) 93% of deaths are in Africa target Malaria Malaria epidemics can occur when: - climate and other conditions suddenly favour transmission in areas where people have little or no immunity to malaria - people with low immunity move into areas Evaluation of the malaria case surveillance system in KwaZulu-Natal Province, South Africa, 2022: a focus on DHIS2. February 2024.Malaria Journal 23(1):47 with intense malaria transmission (e.g. for work or tourism) Malaria epidemic can be very serious if it happens: - in places where malaria is not endemic (people there have no immunity) → will spread fast - only during and after the rainy season → people cannot cultivate the land when they are sick → affects economy https://malariajournal.biomedcentral.com/articles/10.1186/s12936-019-2717-y target Malaria Anti-malarial drug resistance Where anti-malarial drugs have been Treatments: used widely, there are strains of - Anti-malarial drugs: quinine and chloroquine drug-resistant Plasmodium (the drug is - Prophylactic (preventative) drugs, to stop an no longer effective against the infection occurring if a person is bitten by an pathogen). infected mosquito → taken before, during and - Chloroquine resistance: in parts of after visiting an area where malaria is endemic. South America, Africa and South Chloroquine inhibits protein synthesis and East Asia. prevents the parasite spreading within the - Mefloquine resistance: in South body East Asia Proguanil, has the added advantage of inhibiting the sexual reproduction of Plasmodium inside the biting mosquito. - Current best: Artemisinin-based combination therapy (ACT): drugs derived from the plant Artimisia annua, used in combination with another drug, such as mefloquine, to treat infections of P. falciparum. target Malaria Prevention: Break the cycle of transmission! reduce the number of mosquitoes ○ kill the adult mosquito → spraying insecticide, use mosquito nets treated with long-lasting insecticide ○ disturb the habitat and breeding ground: clear the vegetation, drain marshes ○ Kill the larvae: spread oil over the surfaces of water (to make it impossible for mosquito larvae and pupae to breathe) stocking ponds, irrigation and drainage ditches and other permanent bodies of water with fish which feed on mosquito larvae spraying a preparation containing the bacterium Bacillus thuringiensis, which kills mosquito larvae but is not toxic to other forms of life. target Malaria Prevention: Break the cycle of transmission! avoid being bitten by mosquitoes vaccination ○ cover the skin, especially at dusk when ○ Unavailable → still under development stage mosquitoes are usually most active ○ sleep beneath mosquito nets ○ use insect repellents use prophylactic drugs to prevent Plasmodium infecting people, e.g. ○ Pregnant women are treated with a prophylactic drug each time they visit an antenatal clinic in the latter two-thirds of their pregnancy ○ Infants in high-transmission area are given three doses of the drugs when they attend clinics for routine vaccinations warmer Standard precautions were used when performing surgery on a patient positive for human immunodeficiency virus. retrieving HIV/AIDS HIV structure HIV replication in lymphocyte target HIV/AIDS Pathogen: Human Immunodeficiency Virus (HIV) → a type of retrovirus → its genetic material is RNA, not DNA → inside the host, the RNA is converted ‘back’ to DNA (‘retro’) to be incorporated into human chromosomes → latent phase, and can be reactivated target HIV/AIDS Site of action of the pathogen: nucleus T-helper lymphocytes, macrophages, brain cells HIV infects the T-helper lymphocytes and incorporates its genetic material HIV with the cells’ chromosomes → dormant/ latent When the virus is reactivated, it Incubation period: initial multiplies inside the cell and kill it → incubation a few weeks, but up to decrease the number of immune cells → ten years or more before the host becomes unable to defend itself symptoms of AIDS may develop against infection → allowing opportunistic infection: an infection caused by opportunistic infections → non-fatal pathogens that take advantage of a host with a disease becomes severe and fatal weakened immune system, as may happen in someone with an HIV infection target HIV/AIDS Symptoms: Methods of diagnosis: HIV infection – flu-like symptoms and then - testing blood, saliva or urine for symptomless (usually repeated cycle of the presence of antibodies being sick and recovery) produced against HIV AIDS (Acquired Immunodeficiency Syndrome) opportunistic infections including candidiasis, pneumonia, TB and cancers weight loss diarrhoea fever Sweating dementia target HIV/AIDS Transmission: in semen and vaginal fluids during sexual intercourse infected blood or blood products contaminated hypodermic syringes or surgery tools mother to fetus across placenta mother to infant through the mixing of blood during birth mother to infant in breast milk semen /ˈsiːmən/ the liquid that is produced by the male sex organs, that contains sperm (= cells that join with female eggs to make new life) target HIV/AIDS Global distribution: worldwide, Estimated number of deaths from especially in sub-Saharan Africa and AIDS-related diseases worldwide in South East Asia 2017: 940 000 (UNAIDS estimate) Estimated total number of people Adverse effect of AIDS on the living with HIV worldwide in 2017: economic development of countries: 36.9 million (approximately 67% of It affects sexually active people in these in sub-Saharan Africa) their twenties and thirties who are (UNAIDS estimate) also potentially the most economically productive Estimated number of new cases of the purchase of expensive AIDS HIV infection worldwide in 2017: drugs drains government funds. 1.8 million (UNAIDS estimate) target HIV/AIDS Causes of HIV/AIDS epidemic and Challenges in HIV/AIDS eradication: pandemic The virus’s long latent stage Homosexual activity → damage the means it can be transmitted by rectum lining → more prone to people who are HIV+ but who infection show no symptoms of AIDS and Having many sex partners, either do not know they are infected homosexual or heterosexual The virus changes its surface proteins, which makes it hard for the body’s immune system to Other at high risk individuals recognise it → it makes the haemophiliacs who were treated development of a vaccine very with a clotting substance (factor difficult. VIII) isolated from blood pooled from many donors target HIV/AIDS Treatment: How the anti-retroviral drug works: - no cure → e.g. Zidovudine binds to the viral enzyme - drug therapy (with anti-retroviral reverse transcriptase and blocks its action. drug) can only slow down the This stops the replication of the viral onset of AIDS genetic material and leads to an increase → expensive in some of the body’s lymphocytes. → have a variety of side-effects → usually uses combination of several ranging from the mild and drugs, can be complicated temporary (rashes, headaches, → the pattern and timing of medication diarrhoea) to the severe and through the day must be strictly followed permanent (nerve damage, → if not followed well, patient becomes abnormal fat distribution) susceptible to strains of HIV that have developed resistance to the drugs onset: the moment at which something begins, and especially something uncomfortable or unpleasant target HIV/AIDS Prevention: Break the cycle of transmission! DOs DON’Ts maintain abstinence before marriage involved in drug abuse → especially faithful to the partner in marriage if it leads to sharing needles protected sex (if spouse is HIV+) donate blood, if HIV+ contact tracing breastfeed, if HIV+ and from high → offer tests to at risk/ probable income family (who can afford individuals formula milk and the healthcare) ensure sterility of medical devices (needles, scalpels, etc) screen the donated blood for HIV Vaccine If HIV+, handle bleeding carefully, No vaccine is available in the including menstrual blood in female market as it is still in the clinical trial target Tuberculosis (TB) Pathogen: Incubation period: Mycobacterium tuberculosis (bacteria a few weeks or up to several years that infect human cells; → the bacteria are slow growing Mycobacterium bovis (bacteria that infect cattle) Site of action of the pathogen: primary infection in lungs; secondary infections in lymph nodes, bones and gut The pathogen enters the body through inhalation The bacteria live inside the human cells → induce host cell damage damaged lungs → reduced gas exchange capacity target Tuberculosis Symptoms: (of active TB) Methods of diagnosis: racking cough, - rapid molecular test detecting coughing blood, presence of DNA from M. chest pain, tuberculosis sputum sample shortness of breath, - microscopical examination of fever, sputum for bacteria sweating, - chest X-ray Suppressed appetite → - long-term culture of bacteria weight loss (up to 12 weeks) rapid molecular test racking /ˈræk.ɪŋ/ TB diagnosis can take up to very bad and very painful sputum /ˈspjuː.təm/ two weeks! liquid from the passages in your body that go to the lungs culture /ˈkʌl.tʃər/ cells, tissues, organs, or organisms grown for scientific purposes culture of bacteria elaboration → Some types of visa require a TB test Tuberculin Skin Test (TST) or Mantoux Test IGRA (Interferon Gamma Release Assay) target Tuberculosis Transmission: M. tuberculosis : airborne droplets (