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University of Toronto Scarborough
Health Studies
Caroline Barakat

Lecture 10: 1918 Influenza / HIV - AIDS Influenza - history -Hippocrates - record of an influenza pandemic in the year 412 B.C. -Since 1580, there have been 31 additional flu pandemics recorded -Spanish flu of 1918 – 1919 -Spain did not censor how much it impacted the humans -Approximately 50 M deaths worldwide in less than 2 years: - 500,000 death in the US (19,000 in New York City) - 300,000 cases in Ontario - 8700 death (1200 deaths in Toronto in just 3 weeks); 500,000 cases and 14,000 deaths in Quebec Symptoms -Fever, chills, headache, weakness and fatigue as well as coughing, sneezing, runny nose (coryza) -Residual cough and tiredness lasts up to 6 weeks -Complications can include ear infections, pneumonia, dehydration and death -distinctive feature to flu= fever & extreme exhaustion/ fatigue; cold= rare Etiology -3 types of influenza virus: Influenza virus A (most virulent), B, &C (sporadic epidemic between children/young adults) -Influenza A virus has 8 genes 1) genetically unstable 2) Short incubation period 1-3 days 3) Ease of transmission -Spread by droplets – each droplet contains 50,000 – 500,000 virus particles -New & virulent flu strains are produced from the effects of 2 surface proteins -Hemagglutinin (H) – critical to virus entry into cell -Neuraminidase (N)–allows virus to leave & move from cell to cell -There are over 15 H’s and 9 different N’s in bird flu viruses -enters humanscommon among aquatic animals carry influenza in intestine use waterways and excrete feces and if other animals (intermediate host) come into contact with contaminated water, get influenza virus -Virus cannot replicate well in humans unless it moves to intermediate host–usually domestic fowl (chicken, geese, ducks or pigs) -Flu genes of birds, pigs, humans can mix and produces new strains Antigenic drift -humans cannot build immunity -Random mutations that change the genes causing the virus to change Epidemiology -Occurs globally, year-round -Serotypes that have been confirmed in humans (ordered by the number of known human pandemic deaths): -H1N1 - ‘Spanish Flu’ – (refer to end of 2 paragraph, p. 398 of course textbook) -H2N2 - ‘Asian Flu’ -H3N2 - ‘Hong Kong Flu’ -H5N1 - pandemic threat in 2007–8 flu season -H7N7 -H1N2 - endemic in humans and pigs -H9N2, H7N2, H7N3, H10N7 Mode of Transmission Respiratory Droplets - coughing, sneezing or talking Direct Contact – from the hands of an infected person Indirect Contact - by touching surfaces or objects contaminated with the virus Prevention -flu shot protects against targeted or predicted strains -may sometimes get symptoms of flu, but doesn’t prevent from all strains of flu -flu treatments that block the synthesis of N (antiflu drugs) -prevention => clean (wash hands often), cover (cover your cough with tissue), contain (stay clear of others who are sick) HIV/AIDS -AIDS described and first reported in the US in 1981 -Identification of a new human retrovirus HIV-1 in 1983 -1985 – a related HIV-2 virus was discovered -HIV (Human Immunodeficiency Virus) - attacks the immune system -Results in AIDS (Acquired Immunodeficiency Syndrome) - body can no longer fight infection -More than 10 years for the disease to progress from HIV infection to AIDS Etiology -Retrovirus - ‘reverse transcriptase’ -replicate RNA into viral DNA -Two primary strains: - HIV-1: found throughout the world - HIV-2: found primarily in West Africa -Both strains have several subtypes Mode of Transmission -unprotected sex -healthcare settings -transfusion of infected blood/blood products -shared needles or equipment -pregnancy, delivery and breastfeeding Once it enters the bloodstream… -T-Helper lymphocyte (T4 or CD4 cell) -no T-cells able to help and de
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