Between January 1 and April 26 this year, the US saw its highest number of new measles cases since the disease was declared eliminated in 2000.
A bulletin issued by the Centres for Disease Control and Prevention (CDC) records 704 confirmed measles cases since New Year’s Day, all but 44 of them contracted within the US itself.
At the heart of the growing epidemic, researchers led by Manisha Patel of the CDC’s National Centre for Immunisation and Respiratory Disease report, lies one particular type of group.
“Six of the 13 outbreaks were associated with under-immunised close-knit communities and accounted for 88% of all cases,” states the bulletin.
Measles were reported in 12 states and New York City in the first four months of the year, with the majority clustered into 13 outbreaks. Small communities in New York City and New York state constitute the most disease-prone groups, accounting for 474 cases, or 67% of the total.
Almost all of the disease victims across the country were US citizens, with overseas residents accounting for a mere 2%. Some 44 people acquired the disease overseas and brought it into the US – 40 of them unvaccinated American citizens.
Of the 704 cases, almost half – 336 – occurred in children four years old or younger.
Patel and colleagues note that the national immunisation rate for children aged between 19 and 35 months stands at more than 91%, but then issue a stark warning about the growing influence of ant-vax campaigns.
“Unimmunised or under-immunised subpopulations within US communities are at risk for large outbreaks of long duration that are resource intensive to control,” they write.