Vaccines are considered one of the greatest public health achievements of the 20th century. They've saved millions of lives. But there are still outbreaks of vaccine-preventable diseases all over the world — including in the United States.

The Council on Foreign Relations, a nonpartisan think tank, has been tracking news mentions of such outbreaks since the fall of 2008, and they've assembled an amazing, interactive map of them.

In the maps below, each type of illness is identified by a color (Measles / Mumps / Rubella / Polio / Whooping Cough / Other), and larger circles mean more infections (though keep in mind the dots and the maps we've screenshotted here are not all to the same scale).

We've pulled out some interesting things we found as we explored.

Here's a zoomed-out view of all of the vaccine-preventable outbreaks CFR has recorded in North America, with South America, Africa, and parts of Europe and Asia.

Now here's a zoomed-in view of just the U.S.:

Outbreaks naturally cluster where there are more people. Cities with large numbers of people who travel internationally may be especially susceptible, as some — not all — outbreaks originate internationally, especially since some of these infections are more prevalent overseas.

Overall, the United States has seen a huge resurgence in whooping cough in the last few years. Look at the scene from 2009:

Compare the image above to 2012, when all of these whooping cough hotspots popped up. One outbreak in Wisconsin infected almost 6,000 people:

Not vaccinating children is a disturbing trend and a major health risk — unvaccinated children are at least 8 times more likely to get whooping cough than those who have received the recommended pertussis vaccinations. But the CDC says that's not the main reason for the recent spike in whooping cough cases.

The increase is because of "increased awareness, improved diagnostic tests, better reporting, more circulation of the bacteria, and waning immunity," the CDC says. (The whooping cough vaccine gets less effective as we age, which is why boosters are so important.)

On top of the resurgence of whooping cough, 2011 saw measles outbreaks across the country, especially along the Eastern seaboard. These cases were likely due to dropping vaccination rates — 86 percent of those infected were unvaccinated, the CDC reported:

Other than whooping cough and measles, the vaccine-preventable outbreaks in the United States since 2008 involved meningitis, chicken pox, typhoid, tetanus, and mumps. All of these happened in a country where vaccines are widely available and widely used.

But the U.S. is not not alone among developed nations facing an upwelling of vaccine preventable infections. Here's what the maps look like for Australia and Japan:

The United Kingdom has dealt with a surprising number of measles outbreaks, with the largest affecting more than 2,000 people. France has had fewer measles outbreaks overall, but one 2011 outbreak infected almost 15,000 people. And those numbers are dwarfed by rubella outbreaks in Poland and Romania, which infected more than 39,000 and 24,000 people respectively. Here's the relevant slice of Europe:

The largest measles outbreak we found on the map was in the Democratic Republic of Congo, where measles spread to 134,000 people in 2011. A measles outbreak in India infected almost 30,000 people, and one in China infected more than 52,000.

Sierra Leone had a shockingly large outbreak of cholera, a disease that's been completely eradicated in many other countries, and Nigeria (you can see its capital city, Lagos, on this map) seemed to have an especially high concentration of outbreaks overall:

While this could be partially because Nigeria is one of the most populous countries in the world, the country's measles outbreaks are especially troubling since they are associated with very high mortality there.

"Children in [Nigeria, Chad, and Niger]," a 2007 study in the journal PLoS Medicine concludes, "still face unacceptably high mortality from a completely preventable disease."

CFR's full map of vaccine-preventable disease is below. Just click on "map" to play around with it for yourself, or visit the larger version on their site.