I guess that's sort of true, but the actual number for 1947 in NYC was 12 cases. In 1947 Smallpox was well gone from the US. It was still killing in the rest of the world. Suddenly 3 cases appeared; the government quickly enacted a vaccination program and quarantined those people; the total infected reached 12 but the spread of the virus was fully controlled.
The point is it's bizarre to list that particular 1947 small outbreak in NYC as "smallpox" on the chart (everything else on the chart lists worldwide effects). It leads you to think smallpox wasn't a big deal. Au contraire. In the first half of the 20th century, smallpox was still a virulent killer. In fact, it was so common that you would hardly even say it was an "epidemic", it was just constant; hundreds of thousands of people died from it every single year (sort of like Malaria still is) (I guess that's called "endemic").
In fact you can quote a better NYT article on smallpox :
Smallpox killed more people over the ages than any other infectious disease. In the 20th century alone, experts estimate, it took up to a half billion lives, more than all the wars and epidemics put together.
(I'm guessing most of that was in the 3rd world (?) ; the Smallpox vaccine was invented around 1800, but it wasn't eradicated until 1977 ; I haven't seen good numbers on when widespread vaccination was adopted in the 1st world)
The Wikipedia on Smallpox also has this nasty number :
The disease killed an estimated 400,000 Europeans each year during the 18th century
That's 40M in the century, which is a hell of a lot when you consider the low population of Europe in the 18th century. (population of Europe was 100M for almost all of the 18th century, then shot up to 200M near the end with the Industrial Revolution and the growth of cities).
Smallpox is also extremely important historically. The first vaccination was smallpox. (in fact the term vaccination comes from vache or vaca for cow - it was a cowpox , a variant of smallpox, injected as a proxy virus that was less deadly and built the right antibodies).
Smallpox was also the secret weapon of colonists. It's the primary way that Cortez was able to defeat the Aztecs.