Download Lecture 12 - Viral Diseases

5/17/2011
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.
2.
poor lifestyle choices (high fat diets, smoking, lack of exercise)
improved standard of living and healthcare
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WHO 2002 data (note “level of evidence” differences):
Country
Life expectancy
U.S.
78
United Republic of Tanzania
50
Communicable disease deaths (rate)
50
1273
Non communicable disease Non
communicable disease
deaths (rate)
728
267
Question:
What is the likely reason for the dramatic increase in deaths due to heart disease and cancer in 1997 compared to 1900?
1.
2.
poor lifestyle choices (high fat diets, smoking, lack of exercise)
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, ea g o t ose ose es t spa ed t e deous t aces o ts po e ,
leaving on those whose lives it spared the hideous traces of 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
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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
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.
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Smallpox
Science 28 January 2011:
Vol. 331 no. 6016 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)
Accomplishments Polio 4
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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
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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
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
• Acquired by respiratory Acquired by respiratory
route, 2 weeks later see vesicles on skin
• Vaccine established in 1995 for chickenpox
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Interactions of Animal Viruses with Their Host
Herpes simplex‐1
• HHV‐1 causes fever blisters, HHV‐2 genital herpes
• Symptoms: fluid filled skin lesions • Treatment: Acyclovir
Interactions of Animal Viruses with Their Host
• Chronic infections
– Infectious virus can be detected at all times
– Disease may be present or absent during extended times or may develop late
extended times or may develop late
– Best known example
• Hepatitis B
– a.k.a serum hepatitis
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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 b
0% f h h i
di f li
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 groups of infectious agents cause slow infections
Two groups of infectious agents cause slow infections
• Retroviruses, which include HIV, and prions
Virally‐encoded enzyme
Potential target for anti‐viral drugs
Error‐prone (↑ mutations)
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Orthomyxoviridae‐multiple strands of (‐)RNA
• Influenza virus
– Consists of 8 segments of RNA
– Envelope has H spikes (hemagglutinin) and N spikes (neuraminidase)
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
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Structure/Characteristics of Influenza Virus
Structure/Characteristics of Influenza Virus
Hemagglutinin (H)
16? (3)
attachment
Neuraminidase (N)
9? (2)
aids in release
Changes in H and/or N:
antigenic drift
antigenic shift
results in major epidemics
(pandemic flu)
‘68 H3N2
‘77
H1N1
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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
50 ‐ 100 million?
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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 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.
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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 p
prevalent flu strain. The CDC later admitted the vaccine had "no or low effectiveness against ILI (influenza‐like illness).”
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