Veterinary Science and Microbiology
VSC438 Ecology of Infectious
Disease
Viruses
Dr. Jim Collins
Like Small Pox …..
…. Measles is a HUMAN-ONLY infectious agent
The concept of “eradicable” virus disease.
The (world-wide) burden of infectious and parasitic diseases (IPDs)
Much of the underdeveloped world is not only impoverished , malnourished
….but also …. infected
Some world-wide numbers ŕ Measles, Pneumonia, Diarrhea
Are IPDs “population-control” ?
Historic graphs of cases, deaths
Introduction of Vaccine
Measles
Resurgence: Why?
Biology of the virus in the host (pathogenic pathway)
A typical outbreak in the unvaccinated
Resurgence amongst the vaccinated (?) population
1. Indicate what would be necessary to eradicate measles ….or polio.
2. What led to lowering of measles deaths (and many other infectious diseases) before the development of vaccines.
3. Using attack rate figures, explain whether the availability of the measles vaccine in the USA will be effective in eliminating all cases.
4. What factor(s) about the virus/host biology make interrupting transmission of measles difficult?
5. How do we know where the virus comes from in an outbreak? Give examples.
A person had an onset of measles on 13 April
in Mexico. The patient visited Texas on April 10th. A question arose
about the possible exposure of the person to measles in Houston or Dallas, Texas,
USA. But during this year Texas has had only one case of measles in an adoptee
exposed in China with an onset on 14 Feb. They did not have any cases of measles
in the previous year, and in the year before that Texas had 7 cases of which 6
were directly related to international travel.
The incubation period for measles from exposure to rash onset averages 14 days (range 7-18 days). The incubation period from exposure to prodromal illness is 10-12 days with the prodrome usually lasting 2-4 days. Is it possible that this person contracted measles in Texas and carried it to Mexico?