Boo, Boo, Boo: US Measles Cases Increase

This week, the CDC's MMWR reports a total of 131 cases of the highly contagious infection in 15 US states and the District of Columbia from January 1 to July 31 (Table). The overwhelming majority of these cases were imported* (13%) or linked to imported disease (76%). (It is important to note that the number of imported measles cases in the United States has not changed appreciably over the years, but that the number of importation-associated cases accounts for this year's dubious record.) A large percentage (81%) of measles cases were related to 7 outbreaks (≥3 cases). Fifteen individuals, including 4 children younger than 15 months, were hospitalized for disease; however, there have been no deaths—yet. 

Most important, however, is the fact that a whopping 91% of cases occurred in individuals who had not received vaccination or whose vaccination status was unknown. Among these 112 patients, 85% were eligible to receive vaccination, but 66% had declined because of "philosophical or religious beliefs." 

The MMWR highlights outbreaks in 2 locations, Washington state and Illinois, in which affected children had not been vaccinated on the basis of personal-belief exemptions. A sizable portion of these children were home schooled, which obviates the vaccination requirement for traditional-school enrollment.

In an editorial note, the CDC advises that the current national vaccination rate for measles is adequate to prevent the "sustained spread of measles," but that importation-associated outbreaks are likely to continue as long as there are geographic clusters of unvaccinated individuals. Unfortunately this information will probably be used by parents who forego vaccination to maintain their behavior.

Most affected by the deferral of measles vaccination are immunocompromised children and children younger than 12 months of age, who rely on adequate herd immunity. It appears to be a mere matter of time before a measles outbreak will cause a known, severe complication of the disease, like encephalitis or death, in the United States. Such an event has already occurred in the United Kingdom.

* Genetically or epidemiologically linked to cases in Italy, Switzerland, Belgium, India, Israel, China, Germany, Pakistan, the Philippines, and Russia.

Photo of child with measles rash from the CDC.