Viral Diseases. Question: 5/17/2011

Transcription

1 Viral Diseases Question: What is the likely reason for the dramatic increase in deaths due to heart disease and cancer in 1997 compared to 1900? 1. poor lifestyle choices (high fat diets, smoking, lack of exercise) 2. improved standard of living and healthcare 1

2 WHO 2002 data (note level of evidence differences): Country U.S. United Republic of Tanzania Life expectancy Communicable disease deaths (rate) Non communicable disease deaths (rate) Question: What is the likely reason for the dramatic increase in deaths due to heart disease and cancer in 1997 compared to 1900? 1. poor lifestyle choices (high fat diets, smoking, lack of exercise) 2. improved standard of living and healthcare History of Vaccination Smallpox (Variola) smallpox was always present. Filling the churchyards with corpses. Tormenting with constant fear all of those whom it had not yet stricken, leaving on those whose lives it spared the hideous traces tacesof its power, turning babes into a changeling at which the mother shuddered, and making the eyes and cheeks of a betrothed maiden objects of horror to her lover The History of England Thomas Macaulay 2

3 Variolation Smallpox Late 1790 s Edward Jenner developed a vaccine 1967 WHO proposed eradication 1977 last naturally occurring case occurred in Somalia 1980 declared eradicated Smallpox New York Times, 7/30/93 Fate of a Virus A special report; Scientists Debate Destroying The Last Strains of Smallpox The execution of one of the biggest killers in history, the smallpox virus, is being planned for the end of this year. Experts interviewed said it would be the first time any species had been deliberately wiped out. With only 18 weeks until the planned destruction, a last minute debate among scientists over whether the stocks should be kept or destroyed could lead to a stay of execution. The American and Russian governments have the responsibility for destroying the virus stocks, probably by heating them to a very high temperature in an autoclave. 3

4 Smallpox Science 28 January 2011: Vol. 331 no p. 389 Pressure Growing to Set a Date to Destroy Remaining Smallpox Stocks The fate of the world's last stocks of the deadly smallpox virus is once again being debated. Last week, the executive board of the World Health Organization (WHO) began discussing what research remains to be done with the live virus. In May, WHO's governing body, the World Health Assembly, will decide whether to set a firm deadline for the stock's destruction. Contrary to some media reports that the executive board recommended keeping the stocks, no conclusions were reached, says a WHO spokesperson. Vaccines In wealthy countries, a lack of personal experience of infectious diseases has also induced a lack of respect for two of the main weapons that keep them at bay antibiotics and vaccines. Nature 439, 509 (2 February 2006) Polio Accomplishments 4

5 Accomplishments Polio QuickTime and a TIFF (Uncompressed) decompressor are needed to see this picture. Seattle Times, 5/29/2008 Dead at 61 after life in iron lung MEMPHIS, Tenn. For almost 60 years, Dianne Odell lived inside a 7 foot long metal tube, unable to breathe outside of it but determined not to let it destroy her spirit for life. From her 750 pound iron lung, she earned a high school diploma, took college courses and wrote a children's book about a "wishing star" named Blinky. Polio (paralytic) Measles 5

6 Interactions of Animal Viruses with Their Host Persistent infections can be divided into three categories: Latent infections Chronic infections Slow infections Categories distinguished by detection of virus during period of persistence Interactions of Animal Viruses with Their Host Persistent infections Latent infections Infection is followed by symptomless period, then reactivation Infectious particles not detected until reactivation Symptoms of reactivation and initial disease may differ Example Herpes simplex viruses 1 and 2 (HSV1 and HSV2) Shingles (zoster) Varicella (chickenpox) and Herpes Zoster (Shingles) HHV 3 causes chicken pox and latent activation known as shingles Acquiredby respiratory route, 2 weeks later see vesicles on skin Vaccine established in 1995 for chickenpox 6

7 Interactions of Animal Viruses with Their Host HHV 1 causes fever blisters, HHV 2 genital herpes Symptoms: fluid filled skin lesions Treatment: Acyclovir Herpes simplex 1 Interactions of Animal Viruses with Their Host Chronic infections Infectious virus can be detected at all times Disease may be present or absent during extendedtimesormay times may developlatelate Best known example Hepatitis B a.k.a serum hepatitis 7

8 Hepatitis B Incubation period is ~12 weeks 10% of cases become chronic, mortality rate is less than 1% About 40% of the chronic cases die of liver cirrhosis Interactions of Animal Viruses with Their Host Slow infections Infectious agent gradually increases in amount over long period of time No significant symptoms apparent during this time Two groupsof of infectious agents cause slow infections Retroviruses, which include HIV, and prions Virally encoded enzyme Potential target for anti viral drugs Error prone ( mutations) 8

9 Orthomyxoviridae multiple strands of ( )RNA Influenza virus Consists of 8 segments of RNA Envelope has H spikes (hemagglutinin) and N spikes (neuraminidase) Incubation is 1 3 days Symptoms include: chills, fever, headache, muscle aches, may lead to cold like symptoms Structure/Characteristics of Influenza Virus Segmented genome Hemagglutinin (H) attachment Neuraminidase (N) aids in release Changes in H and/or N: antigenic drift antigenic shift 9

10 Structure/Characteristics of Influenza Virus Structure/Characteristics of Influenza Virus Hemagglutinin (H) attachment Neuraminidase (N) aids in release 16? (3) 9? (2) Changes in H and/or N: antigenic drift antigenic shift results in major epidemics (pandemic flu) 68 H 3 N 2 77 H 1 N 1 10

11 Influenza complications bacterial pneumonia (secondary infection) viral pneumonia stress on heart and lungs severe epidemic 40,000 people die (very young, very old) 1918 epidemic 1918 influenza epidemic 1/2 million in U.S. (often young adults) 20 million deaths worldwide million? 11

12 Prevention/Treatment of Influenza vaccine developed for upcoming year based on circulating H and N types vaccine strains are grown in chicken eggs, harvested, and then inactivated attenuated vaccine recently introduced treatment (influenza specific medications) amantadine, rimantadine interfere with uncoating process neuraminidase inhibitors (Tamiflu, Relenza) Prevention/Treatment of Influenza The single best way to protect against the flu is to get vaccinated each year. There are two types of vaccines: The "flu shot" an inactivated vaccine (containing killed virus) that is given with a needle, usually in the arm. The flu shot is approved for use in people older than 6 months, including healthy people and people with chronic medical conditions. The nasal spray flu vaccine a vaccine made with live, weakened flu viruses that do not cause the flu (sometimes called LAIV for "live attenuated influenza vaccine" or FluMist ). LAIV (FluMist ) is approved for use in healthy* people 2 49 years of age who are not pregnant. 12

13 Prevention/Treatment of Influenza From an article on the Web: Early in that outbreak, the Centers for Disease Control and Prevention (CDC) recommended even more widespread vaccination, without pointing out until much later that the vaccine then available "might not" do anything to protect the public against the prevalent flu strain. The CDC later admitted the vaccine had "no or low effectiveness against ILI (influenza like illness). 13