Expert: Florence M Rollwagen - 6/9/2009

Question
What features of small pox made its eradication possible where as we have made little progress in eradicating other infectious diseases such as Tuberculosis & Influenza?

Answer
Hi Anitha:  Thanks for your question.

There are several differences in infectivity between smallpox and the other two.

First, human smallpox does not infect other species, so there is no reservoir of infection, so a vaccinated person is protected for his whole life.  It's easy to vaccinate, so unsophisticated populations can do it easily.  New generations can't be exposed to it because it infects only humans.

Second, influenza has a reservoir in the wild (birds) and it changes rapidly from one generation to another.  That's why this year's flu vaccine doesn't protect against next year's.  Besides, the vaccine has to be given by needle, hard to do in uneducated populations.

Third, TB does have a vaccine (BCG), but the rapid evolution of drug resistant TB eliminates BCG as a vaccine.  Treatment for TB requires multiple drugs given over a long period of time, again, hard to do in rural and uneducated populations.

Here's a report from the Centers for Disease Control (CDC) on eradication of diseases:
http://www.cdc.gov/mmwr/PDF/rr/rr4216.pdf

Hope this helps!

FM Rollwagen, PhD