Tag: investigating an outbreak

How Do They Figure out Who Starts an Outbreak?

As we continue to see outbreaks of vaccine-preventable diseases in the post-vaccination era, it is important that these outbreaks be quickly contained.

But it is important to understand that these outbreaks don’t simply stop on there own. A lot of work goes into containing them.

Working to Contain an Outbreak

And that work containing outbreaks is expensive. Much more expensive than simply getting vaccinated.

For example, the total personnel time and total direct cost to the New York City Department of Health and Mental Hygiene responding to and controlling the 2013 outbreak in NYC were calculated to be at least $394,448 and 10,054 personnel hours.

Why it is so expensive is easy to see once you understand all of the work that goes into containing an outbreak. Work that is done by your local health department as soon as a case of measles, or other vaccine-preventable disease, is suspected.

Work that, for a measles outbreak for example, includes:

  • initiating a case and contact investigation
  • quickly confirming that the patient actually has measles, including testing
  • assessing the potential for further spread – identifying contacts who aren’t immune to measles and are at risk for getting measles
  • isolating people with measles and quarantining contacts who aren’t immune to measles for at least 21 days after the start of the measles rash in the last case of measles in the area, including everyone who is intentionally unvaccinated
  • offering postexposure vaccination, a dose of the MMR vaccine within 72 hours of exposure to contacts who are not fully immune so that they can get some protection maybe don’t have to be quarantined
  • having targeted immunization clinics in the affected population, such as a school or church, to get as many people vaccinated as possible, even after 72 hours, so they have can be protected in the future

That’s an awful lot of work.

Work that continues until the outbreak officially ends.

Finding the Source of an Outbreak

Another big part of the work that goes on to contain an outbreak is identifying the source of the outbreak.

Was it someone who had recently been traveling overseas, a visitor from out of the country, or someone that was already part of an another outbreak?

Why is that so important?

If you don’t find the source of the outbreak, then you can’t be sure that you have found all of the people that have been exposed, and the outbreak might go on for an extended period of time.

And no, it is never shedding, a vaccine strain, or a recently vaccinated child that causes these measles outbreaks.

Anatomy of a Measles Outbreak

A closer look at the measles outbreak in San Diego, California in 2008 can help folks understand even better what happens during one of these outbreaks.

A 7-year-old who is unvaccinated because his parents have a personal belief vaccine exemption travels to Switzerland with his family.

A week after returning home from the trip, he gets sick, but returns to school after a few days. He then develops a rash and sees his family physician, followed by his pediatrician, and then makes a trip to the emergency room because he continues to have a high fever and rash (classic measles symptoms).

He is eventually diagnosed with measles, but not before eleven other children are infected with measles. This includes two of his siblings, five children in his school, and four children who were exposed at his pediatrician’s office.

It is not as simple as that though.

During this measles outbreak:

  • Three of the children who became infected were younger than 12 months of age, and were therefore too young to have been vaccinated
  • Eight of the nine children who were at least 12 months old were intentionally unvaccinated because they also had personal belief vaccine exemptions
  • About 70 children were placed under voluntary quarantine for 21 days after their last exposure because they were exposed to one of the measles cases and either didn’t want to be vaccinated or were too young
  • One of the infants with measles traveled to Hawaii, raising fears that the measles outbreak could spread there too

All together, 839 people were exposed to the measles virus.

This family didn't have a choice about their son getting sick - he was too young to be vaccinated when he was exposed to an unvaccinated child with measles.
This family didn’t have a choice about their son getting sick – he was too young to be vaccinated when he was exposed to an unvaccinated child with measles.

At least one of them was a 10-month-old infant who got infected at his well child checkup, was too young to have gotten the MMR vaccine yet, and ended up spending three days in the hospital – time his parents spent “fearing we might lose our baby boy.”

The parents of this 10-month-old weren’t looking for a vaccine exemption and didn’t want their child to catch measles, a life-threatening, vaccine-preventable disease. Instead, they were counting on herd immunity to protect him until their child could be protected with an MMR vaccine. They were one of “those who come into contact with them” that got caught up in a decision of some other parents to not vaccinate their child.

The kids who are at risk and get a vaccine-preventable disease because they are too young to get vaccinated, have an immune system problem that prevents them from getting immunized or their vaccine from working, and the kids who simply didn’t get protected from a vaccine are the hidden costs of these measles outbreaks that we don’t hear about often enough.

What to Know About Finding the Source of an Outbreak

Without all of the hard work that goes into containing outbreaks, the outbreaks of measles, pertussis, mumps, hepatitis A, and other vaccine preventable diseases would be even bigger.

More on Finding the Source of an Outbreak