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Two Jewish men in New York (Flickr by Kynan Tait). The site of 2009/10's near-4,000 large mumps outbreak |
It started
during the middle of 2009 when an eleven-year old boy returned home to the U.S from a holiday in the UK. The UK was just experiencing
an exceptionally large (about 7,500 people) outbreak of mumps that year but don't worry, that boy had been twice vaccinated with the MMR immunisation. He should be OK. Shouldn't he?
As it turns out, he wasn't and he became infected with the mumps virus. And so our three year-long story begins.
The problem was that by the time this now mumps-infected boy realised he was ill (fever, swollen glands, potentially inflammation of the testicles and meningitis) he was attending a youth camp in New York along with 400 other orthodox Jewish boys. Unluckily for us, the mumps incubation period can be over 2 weeks and you can be infectious up to one week before this, making it particularly hard to contain as we will see.
A couple of days later the camp ended and each one of those mumps-exposed, potentially infected children were seeded back into society. By the time it had subsided nearly one year later, 3502 cases of mumps had been observed across the state of New York, the biggest outbreak the US had seen in decades and it was most likely attributable to this single index patient who brought the disease in from the UK.
But what was most worrying was that 76% of them had been immunised with two doses of the MMR vaccine, our mainstay of protection against the virus. So just how could mumps get passed this defence and cause such a massive outbreak? It took the U.S Centers For Disease Control and Prevention nearly 3 years to find an answer. The investigation is published in the New England Journal of Medicine
here.