main article image
(FRED Florida Measles Simulator)

This Chilling Simulation Shows What a Measles Outbreak Could Do to Your City

PETER DOCKRILL
15 MAY 2019

Measles is exploding in all the wrong ways right now. Hotspots throughout the US reveal the most at-risk communities, but the really scary thing is that this growing crisis is far from just a local issue.

 

If the worst were to happen, and an outbreak were to land on your doorstep, what would it look like? You don't have to imagine the consequences. Scientists have already crunched those numbers for you.

A simulation tool developed by researchers at the University of Pittsburgh – and recently updated in a collaboration with the University of South Florida (USF) – gives a disturbing glimpse at what can happen in a real-life measles epidemic.

Last month, this simulation system – called FRED (A Framework for Reconstructing Epidemiological Dynamics) – was customised with actual school vaccination data for the state of Florida, to realistically represent the infection risks faced by individual schools in each Floridian county.

"It's just not words, it's just not data, it's just not numbers that people are listening to," says USF public health researcher Karen Liller.

The researchers note that the simulation – which is designed to illustrate the way herd immunity operates – shows the upper limit of measles cases that could plausibly be expected to occur in an outbreak, and doesn't anticipate the effects of any public health interventions during an emergency.

Nonetheless, based on Florida vaccination data at county or metropolitan area level, the tool reveals what could actually happen if a single student with measles attended schools in the locality – alongside a separate simulation showing what an epidemic might look like if the vaccination rate in schools in the same place were decreased by 10 percent.

 

That single 10 percent drop might not sound like much, but given the way herd immunity functions, it makes for a drastic contrast in the sickliness of the state's student body.

Take DeSoto, FL for example. After 266 days of exposure, the addition of just one measles-infected student to just one of DeSoto's schools would result in nine extra cases of measles, based on the county's current measles vaccination rates.

But if those rates were to drop by just 10 percent from what they are now, it'd be a whole different ball game: suddenly, the decrease in overall immunity would mean DeSoto would be presented with almost 800 new cases of measles (almost 90 times as many illnesses).

That's a pretty alarming disparity, but the sad truth is that's the kind of thing we're up against in 2019 in the US – a year which has already eclipsed the entirety of 2018's measles infections (and it did so just three months into the year).

Other regions in Florida fare even more poorly under pressure. In the Miami-Fort Lauderdale-West Palm Beach area, 111 measles cases could result, based on the current vaccination rates.

 

If those rates slip by 10 percent though, a stunning 54,476 people could be struck by the disease.

"And the concern there, of course, is when you have those number of cases, how long will it take before it exhausts the public health system?" Liller asked the Orlando Sentinel.

FRED isn't limited to Florida alone, however. The simulator can actually project the spread of measles epidemics across any state in the US, based on generalised 80 percent vs 95 percent vaccination rate calculations.

"In most cases, the difference between the 80 percent coverage scenario and the 95 percent coverage scenario is quite dramatic," the FRED team explains.

"This shows the importance of a high vaccination rate in providing protection for the entire community."

Have a go here and watch the results unfold yourself. This is what nonchalance – let alone dangerously ill-informed, anti-vax views – about infectious diseases could one day bring about in the places we live.

Even the researchers who developed the simulator are taken aback.

"I was amazed," Liller told WFLA News.

"Measles is just so infectious that one person can infect 18 others, but to watch how rapidly it could spread in our community is incredible."

The US-wide FRED Measles Simulator is available for you to try here, and the Florida-specific version can be found here.