SPHU 1020: week of 3.7.16 notes
SPHU 1020: week of 3.7.16 notes SPHU 1020
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This 5 page Class Notes was uploaded by Claire Jacob on Friday March 11, 2016. The Class Notes belongs to SPHU 1020 at Tulane University taught by Dickey-Cropley, Lorelei in Summer 2015. Since its upload, it has received 25 views. For similar materials see Cell, Individual & The Community in Public Health at Tulane University.
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Date Created: 03/11/16
Tuberculosis Tx and Prevention ● For TB infection, isoniazid for 6 months is completely effective Noncompliance is a serious problem ● Remains problematic even if antibiotics are provided for free ○ 25% of the homeless in London and San Fran are infected by TB ○ Supplying infected individuals with takehome drugs has been unsuccessful ○ Leads to antidrug resistant strains ● DOTS (directly observed treatment) people go to their house to make sure that they take the drugs ○ Combates noncompliance and complacency ○ Requires microscopy, drug supplies, direct observation, and surveillance and monitoring ○ Once TB is found in sputum, health workers must watch the patient swallow the full course of the prescribed antibiotics every day ■ Sputum is retested after 2 months and again at 6/8 months ■ Become noninfectious within 24 weeks ○ Costeffective and has cure rates of 8590% ○ Longer duration for those with multidrug resistant TB ● Keeps evolving because TB and the drugs used to treat it have been around for a very long time Prevention ● Vaccine ○ The BCG vaccine for tuberculosis is controversial ■ Vaccine consists of attenuated (weakened) live tubercle bacilli ■ Protection rate is about 80% in children and less than 50% in adults ■ Protection is not lifelong, lasting only 515 years ■ Those vaccinated will test positive for the tuberculin skin test ○ New approaches utilizing recombinant DNA technologies in vaccine development are promising for the future ● DOTS implementation ○ Needs to be adopted by more countries ● Improved social conditions ○ Many in the world live in abject poverty and suffer from a lack of clean water, malnutrition, and inadequate housing conditions The Case of Andrew Speaker Influenza Biology of Influenza Infects humans and other species (seals, pigs, birds, dogs) Virus, so it evolves with us… this is how we get the different strains History of influenza 412 BC- first mentioned by Hippocrates 1580- first pandemic described 1580-1900- 28 pandemics Transmission Transmitted easily through droplets/ aerosol by sneezing, coughing o 100,000 to 1,000,000 virions per droplet Influenza in humans closely tied to seasonal outbreaks, typically associated with winter months o Conditions of cooler temperatures and low humidity favor transmission Crowding, close intermingling favors transmission Fomites/other people play secondary role o Expelled respiratory droplets can contaminate surfaces, and be transmitted to mucous membranes through direct contact o Also touching infected person with virus and then touching eyes Handling infected birds Complications: Influenza death ~23,607 deaths per year o Rates fluctuate yearly o Deaths peak when H3N2 strain of influenza A dominates. When it’s H1N1 B, deaths lower Recently some increase in morbidity and mortality- possible factors? o More elderly people o More high risk neonates o More immunosuppressed patients Pneumonia most frequent complication, especially secondary bacterial pneumonia o Bacterial superinfection can be severe Streptococcus pneumonia most common pathogen involved but Staphylococcus aureus increasing, especially severe pneumonia d/t MRSA Strains Has two types of surface antigen protein spikes o H (hemagglutinin) spikes attach the virus to epithelial cells of the respiratory mucosa and aid in viral entry into these cells o N (neurominidase) spikes play a role in release of new virions from cells Influenza A, B, and C Influenza A Starts as avian (bird) influenza virus Drift and Shift Antigenic shift (type A only), major, abrupt, antigenic change in H or N spikes o Rapid evolution of new strains so different that most people don’t have immunity o Result from recombination of genetic material from cells infected with different viral strains o Happens only occasionally o Pig (blender) is infected with A and B which combine into a new strain… this creates a new, mutated virus Antigenic drift Occurs among influenza A viruses o Results in new variants of prevailing seasonal winter strains yearly o Results from slow accumulation of mutations affecting antigenicity of H and N antigens o Why we require new vaccine yearly o Some years are worse than others—partly related to degree of “drift” Specific antibodies against the H and N proteins are protective, but these proteins are capable of rapid evolutionary change Prevention Vaccine o Current CDC guidelines recommend immunizing the elderly, pregnant women, and high risk patients (health care and lab workers, immunosuppressed) Influenza Vaccines/Tx Influenza antiviral drugs o Block influenza neuraminidase activity o Must be taken within 48 hours after symptoms to reduce severity of illness Zanamivir (Relenza, FDA approved) Peramivir Oseltamivir (Tamiflu) What is an influenza pandemic Influenza pandemics are worldwide epidemics of a newly emerged strain of influenza Compared to seasonal influenzas, pandemic influenzas infect more people, cause more severe illness, and cause more deaths o Few, if any, people have any immunity to the new virus Allows new virus to spread widely, easily, and to cause more serious illness o Seasonal influenza viruses most often cause severe disease in the very young, the very old, and those with chronic illnesses, but pandemic influenza strains can infect and kill young people Flu Pandemic of the Twentyfirst century Major pandemics occurred in 1918 (highest mortality rate), 1957, 1968 Bird Flu Scares World currently faces potential pandemic threat of avian (bird) flu cause by H5N1 strain o From poultry o Fear that an adaptive strain will allow sustained transmission from human to human o H5N1 is a new virus, hence, human population has no immunity Lessons from past pandemics Occur unpredictably, not always in winter Great variations in mortality, severity of illness, and pattern of illness or age most severely affected Rapid surge in number of cases over brief period of time, often measured in weeks Tend to occur in waves of 6-8 weeks, subsequent waves may be more or less severe Key Lesson: unpredictability Easy to spread worldwide now because of air travel Would the next pandemic be severe? Study past pandemics to predict future ones What can be done to slow spread of a pandemic? Vaccine o “pre-pandemic” H5N1 vaccines are in development, but would have reduced efficacy in a pandemic due to antigenic drift o specific vaccine cannot be made until strain has been identified, and it takes at least 4-6 months to produce Antivirals o Likely to be only major medical countermeasure available early in a pandemic o Uncertainty about effectiveness for treatment or prevention o U.S. goal is to stockpile enough antiviral drugs to treat 25% of U.S. population Disease containment measures o May be the only measures available in early stages of a pandemic o May be helpful in slowing spread from country to country Disease containment measures Isolation: restriction of movement/separation of ill infected persons with a contagious disease Quarantine: restriction of movement/separation of well persons presumed expose to a contagious disease Self-shielding: self-imposed exclusion from infected persons or those who may be infected Social distancing Snow days Other methods: Hand hygiene (cleaning hands) Respiratory hygiene “cover your cough” Cleaning and disinfection of contaminated objects, surfaces Physical barriers (glass or plastic windows to protect front desk workers) Use of personal protective equipment (PPE) in some setting such as gowns, gloves, eye, and mouth protection Global surveillance and planning Current WHO phase of pandemic alert for avian influenza A is: ALERT Global surveillance looking for the flu Have programs ready to be launched in case of emergency
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