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HLTA01 Lec 10

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University of Toronto Scarborough
Health Studies
Caroline Barakat

Lecture 10: Influenza/HIV-AIDS Influenza – History  Can be dangerous (became pandemics)  Hippocrates - record of an influenza pandemic in the year 412 B.C.  Since 1580, there have been thirty-one additional flu pandemics recorded  Spanish Flu (1918 - 1919) b/c Spain did not provide any censorship of how many cases and people were affected.  Not only affected soldiers, but civilians as well  Approximately 50 M deaths worldwide in less than 2 years (1918-1919)  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 Video:  Spanish flu:  Cause by virus  20 million people died (more than the first world war)  If there wasn’t war, strain would have be kept isolated  Originated from US who made their way to France and other countries trading materials as well as the flu  It took 17 days to spread  Wearing face masks, carrying garlic and onion to help prevent it, but they left their nose exposed where they were most likely to catch it Symptoms  High fever, chills, headache, weakness and fatigue as well as coughing, sneezing, runny nose regular cough but it is different because these symptoms come suddenly  Residual cough and tiredness, depression lasts up to 6 weeks  Complications can include ear infections, pneumonia, dehydration and death Etiology  3 types of influenza virus: Influenzavirus A (most virulent), B, &C  Influenza A and C infect multiple species (a and c can mixed together and form a new virus), while influenza B almost exclusively infects humans (b and c sporadic and affects young children and old)  Influenza A virus has 8 genes o Because there is constant mixing/mutation in different species  New and virulent flu strains are produced mainly from the effects of two surface proteins  Hemagglutinin (H) – critical to virus entry into cell  Neuraminidase (N) – allows virus to leave host cell after replication and move from cell to cell  There are over 15 H’s and 9 different N’s in bird flu viruses (don’t cause harm and are excreted through feces, but whoever comes across the feces will become infected in domestic birds and give it to humans)  Flu virus from birds - unable to replicate well in humans unless they move to an intermediate host: chickens, geese, ducks  Flu genes of birds, pigs, humans can mix and produces new strains  We know that flu virus is contagious :A10 (Can infect 10 people) rnot is 10  Pandemics occurs 2-3 time per century  Before one wave of influenza is done, another kind can come again (hard to find a vaccine because it mutates) Antigenic drift  Random mutations that change the genes causing the virus to change  The genetic composition of the new strain is mixed with genes of avian strain and human strain Epidemiology  Occurs globally, year-round (more temperate areas (colder climates), where it is more enclosed with less ventilation  Serotypes that have been confirmed in humans (ordered by the number of known human pandemic deaths): o H1N1 - ‘Spanish Flu’ – (refer to end of 2nd paragraph, p. 398 of course textbook)doesn’t mean that this is the same H1N1 as now because there isn’t the same amount of damage o H2N2 - ‘Asian Flu’ o H3N2 - ‘Hong Kong Flu’ o H5N1 - pandemic threat in 2007–8 flu season o H7N7 o H1N2 - endemic in humans and pigs o H9N2, H7N2, H7N3, H10N7 o Happens in Asia more often because humans come in contact with their domesticated animals more than other countries Video:  Spanish flue the same as H1N1?  This strain is different from spanish flu  Spanish had specific destinations  The name is just a technical name and has the same number of H and N Mode of Transmission  Respiratory Droplets - contain the virus and are expelled into the air by coughing, sneezing or talking and enter the body through a person’s mucous membranes (e.g., nose, mouth).  Direct Contact – the virus spreads from person-to-person from the hands of an infected person. A person touches their mucous membranes with their contaminated hands.  Indirect Contact - The virus spreads from one person to another by touching surfaces or objects contaminated with the virus. A person touches their mucous membranes with their contaminated hands.  Flu shot is encouraged, but only protects from the strains that are targeted  Some vaccine shows symptoms, but it really protects the elder HIV/AIDS  In late 70s there was increase rate of homosexual diseases and some sort of pneumonia that turned into HIV  HIV (Human Immunodeficiency Virus) - attacks the immune system resulting in chronic, progressive illness that leaves people vulnerable to opportunistic infections and cancers  Results in AIDS (Acquired Immunodeficiency Syndrome) when the body can no longer fight infection due to HIV  On average, it takes more than 10 years for the disease to progress from HIV infection to AIDS  AIDS was first reported in the US in 1981, a related virus HIV II was described in 1985  Related to methods to dealing with HIV/AIDS with drugs in US and UK o using clean needles, etc Etiology  HIV is a retrovirus; contains an enzyme ‘reverse transcriptase’; replicates to produce viral DNA from its RNA genome (able to change RNA to DNA and do the damage to immune system  Two primary strains:  HIV-1: found throughout the world  HIV-2: found primarily in West Africa, where the virus may have been in circulation since the 1960s - 1970s because it was found in blood banks that were stored.  Both strains have several subtypes Mode of Transmission  Virus must enter the bloodstream o unprotected sex o occupational exposure in health care settings (through transfusion) o shared needles or equipment for injecting drugs, tattooing, skin piercing or acupuncture o Transplacently: pregnancy, delivery and breastfeeding (i.e. from an HIV-infected mother to her infant) Once it enters the bloodstream…  It attacks immune system (white blood cells called T4 or CD4)  HIV makes co
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