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Simulation shows how the spread of Measles could be fast and terrifying

Modelling of a measles epidemic reveals the terrifying possibilities of a common disease to wreak havoc on our world.

Aug 8, 2019 |
4 min read

As the 20th Century wore on and crossed over into the 21st, people became pretty blasé about the dangers to be faced from diseases like chickenpox, measles, and mumps.

But the evidence is increasingly suggesting that the Western world might need to prepare itself for the worst, given the falling vaccination rate and rise in measles outbreaks, and new computer simulation is now available to show you exactly how bad the worst could be.

The US-designed simulation system creates a frankly horrifying picture of what would happen if a measles epidemic struck a major US city. And the results are really not pretty.

The simulation has been given the rather disarmingly cozy name of FRED (an acronym for Framework for Reconstructing Epidemiological Dynamics, obviously…) and was developed by a team at the University of Pittsburgh, updated with help from the University of South Florida with accurate vaccination data from Florida schools.

The simulation creates a scenario at a school where a single measles infected student is in attendance, modeling what would happen if vaccination rates were just 10% below the current norm. In the sample of a school in Desoto, a 10% drop in vaccination could lead to 90 times the number of infections, with 800 people infected from just one measles-carrying student.

In more densely populated areas it could be even higher, Fort Lauderdale seeing over 50,000 infections with a 10% drop in vaccination. With these sorts of numbers, it wouldn’t be long before the local public health system would be utterly overwhelmed.

This should come as a wake-up call to the so-called anti-vaxxers, who have spent the last just over twenty years building up a head of steam against the vaccination of children. Initiated by some very quickly debunked research by Andrew Wakefield, the MMR vaccine for dealing with measles, mumps, and rubella was erroneously linked to autism in children.

In these more autism spectrum disorder aware times, the idea of even being afraid of autism seems a little ridiculous, let alone the sense that it can be spread or imposed by an injection.

However, the anti-vax movement has only gained in strength since then, feeding on more or less wild conspiracy theories spread through forums and social media about the purposes and harmful effects of childhood vaccines.

By 2010, according to Gary S Marshall of the University of Louisville School of Medicine, over half of the parents feared that vaccines were harmful, and roughly a quarter believed that they caused autism.

Unsurprisingly Marshall’s study showed that 86% of sampled doctors had experienced some form of vaccine refusal, and over 50% had experienced outright rejection by parents to vaccinate their children.

This skepticism is already seeing a knock-on effect. Globally, measles outbreaks have been seen on a scale not seen since 1992, not just in the increasingly vaccine-skeptical United States, but in Ukraine, India, Pakistan, the Philippines, Yemen, Brazil, and Israel.

The US alone saw more measles infections in the first three months of 2019 than in all of 2018. Overall there has been a 300% increase in global cases since 2018, and it may only be a matter of time before outbreaks occur in countries not yet obviously affected.

In some of these countries lack of access to health care and vaccines is at issue, but the growing trend of vaccine refusal is unquestionably a factor.

The invisibility of measles is one reason for this refusal. Because the west has so successfully kept a lid on this almost uniquely infectious disease, the sense of its danger has diminished accordingly. And, because vaccinations have caused outbreaks not to occur, it has become easy to assume that measles outbreaks can’t happen.

Part of the problem is that humans are really very bad at judging risk, the majority of the population are not especially numerate, and this can make them bad at extrapolating from statistics or making calculations of threats to them and their loved ones.

By and large, people are more influenced by anecdotes (a form of evidence that science rightfully holds in low regard) rather than by abstract numbers and the higher the emotion or perceived personal threat in those, the more likely they are to react.

As such the FRED modeling system may be a useful way to shock parents into seeing themselves in the statistics and realizing the threat that measles may pose to them, their loved ones, their city and their way of life is dangerous and severe.

But the real threat is lack of what is known as herd immunity. Herd immunity means having enough people vaccinated against a disease that it prevents any chance of it being spread to even the unvaccinated (like newborn babies or those with vaccine allergies).

For herd immunity to be effective against measles, between 90 and 95% of the population, adults, and children, need to be vaccinated. And, in certain hotspots, including in New York City and state, that just isn’t happening anymore.

This is what these FRED simulations show, a scenario where herd immunity has dropped below safe levels.

“In most cases, the difference between the 80 percent coverage scenario and the 95 percent coverage scenario is quite dramatic,” the team explain. Even Karen Liller, the public health researcher for the University of South Florida, was taken aback by what the simulations showed. ”

“Measles is just so infectious that one person can infect 18 others,” she says, “But to watch how rapidly it could spread in our community is incredible.”

If you want to take comfort from the flaws in the model, the researches acknowledge that it is a worst-case scenario model and doesn’t account for any public health interventions that local governments might (and most probably would) make.

But nonetheless, it’s a troubling picture that the computer models. All the more troubling for how likely they might be, someday, to be proved correct.

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