The CDC just announced its final 2014 measles case numbers. They have reported 644 cases for 2014, the highest number of measles cases in any year since measles was declared eliminated in 2000. The graph below shows measles cases since 2001 up to November 29, 2014.
December ended with a bang: between December 15 and December 20, visitors to Disneyland in Anaheim, California, were exposed to measles courtesy of an as-yet-unidentified index case. Related measles cases have been reported in California (22 so far), Utah (2), Washington (1) and Colorado (1). From November 29 to December 31, a total of 31 measles cases were reported across the country.
And 2015 was to off a bad start for measles, for several reasons. First, the cases will likely continue to climb related to exposures to people who were infected at Disneyland. The LA Times reports a variety of exposure opportunities for people in Long Beach and San Bernardino between January 3 and January 8 (see the list here). An unrelated outbreak in Mitchell, South Dakota (population 15,000), had its first reported case on December 30. Today, 13 cases are included in that outbreak, 9 of them in Mitchell-area residents and 4 in out-of-state residents (the latter includes the index case, an unvaccinated adult male resident of Kansas who had traveled to South Asia).
I spoke with infectious diseases physician and History of Vaccines Advisor Thomas Fekete, MD, about his impressions of the current measles outbreaks. He noted that measles is contagious in ways that some of our bigger worries, such as Ebola, are not–meaning that it is spread via airborne transmission and is highly contagious. Moreover, measles spread is entirely in our own hands and we cannot blame vectors such as monkeys, bats, ticks, or mosquitoes.
Dr. Fekete said, “Vaccination is a great way to interrupt transmission, but it can be overwhelmed in high-exposure settings since it doesn’t take much to continue an outbreak in a partially immunized population. The death of measles 20 or 30 years ago was much exaggerated–it was a mix of wishful thinking and altering the case definition to require lab confirmation rather than clinical impression, hence making diagnosis more difficult to corroborate.”
Finally, Dr. Fekete noted that even a state with very low population density like South Dakota is at risk because of the tendency of people who are susceptible to congregate together at times when one person is infectious. Indeed, the South Dakota cases have so far been confined to a single extended family that does not immunize.
Clearly, ongoing measles outbreaks across the globe and measles vaccine refusal here in the United States mean that overstrapped state public health departments will continue to spend time and money tracking cases for the foreseeable future.