Austin officials combat measles outbreak with data-driven simulator

As the measles outbreak in Gaines County in West Texas began to spread in February, Austin Public Health and University of Texas officials were working behind the scenes to lead the country in how to forecast the spread of measles based on school vaccination rates.

West Texas has now had 753 confirmed cases of measles since January, but Travis County has only had two, Hays County one and Williamson County six.

On Feb. 12, Austin Public Health's Dr. Desmar Walkes, the public health authority for Travis County, called up thought leaders who had helped Austin get through the COVID-19 pandemic with a lower death rate than most cities its size. Those leaders included UT's Lauren Ancel Meyers, who leads the Centers for Disease Control and Prevention's Center for Forecasting and Outbreak Analytics; epiEngage, a group of academic researchers and public health representatives; and UT's Center for Pandemic Decision Science. Meyers also led the COVID-19 Modeling Consortium and is the co-founder for the Center for Advanced Preparedness and Threat Response Simulation.

"We had a lot of practice in COVID turning things around on a dime," Meyers said. It was time to do that again.

Through the UT-based epiEngage network, "we are constantly trying to build better tools and trying to get these tools in the hands of the public health professional," she said.

The group wanted to accurately model how a measles infection might spread, especially through schools. Schools were identified as a key place for transmission because the younger age group was the most unvaccinated and the most vulnerable to getting measles.

By Feb. 18, Meyers' team at UT had a mockup for a website to calculate the risk of an outbreak based on the size of a school, the number of the initially infected people and the school or school district's vaccination rate. By Feb. 26, they had a working demonstration model, which they demonstrated to Austin Public Health as well as public health agencies in Houston, El Paso, and New York City, and to researchers at Johns Hopkins University and the CDC.

By March 3, Meyer's team was showing the Austin school district what the calculator could do, and then it fully launched the epiEngage Measles Outbreak Simulator on March 4.

In the meantime, Austin reported its first case of measles, an infant who had traveled out of the country and was quarantined, on Feb. 28. A second case in May, also from travel, but in an adult, was also able to be quarantined quickly.

"Right now, it looks like things have quieted down in Texas," Meyers said. "It doesn't mean that the risk is gone. The risk of measles outbreak does relate to the level of vaccination. In communities and schools were vaccination rates are well below 90%, those communities are quite vulnerable to outbreaks."

The state data the calculator uses is broken down by county, by school district and by private school.

Seeing the numeric possibilities

The simulator, though, helped Austin Public Health and the Austin district target some of the schools with the lowest measles, mumps and rubella vaccination rates to bring up those rates. The goal for vaccination is to have 95% of the population vaccinated to prevent a disease from having a space to spread in the community.

"In communities where vaccination rates dip even slightly, the risk of measles outbreaks rises dramatically," Walkes said. "This new measles calculator puts that reality into stark relief, showing how fast measles can spread and making the invisible visible. It’s a vital tool that empowers schools, health care providers and families to act now, keep students safe and strengthen our collective immunity."

In Travis County, the measles vaccinations rates for all kindergartners have slipped from 96.2% in the 2019-2020 school year to 89.6 in the 2023-2024 school year.

With this targeted approach, some at-risk Austin school district elementary schools with vaccination rates of 86% were able to get to above 90%.

Using the simulator, for a 700-student Austin elementary school, one infected kid has a 62% chance of becoming more than 10 measles cases. The size of the outbreak is likely to be between 83 and 111 among unvaccinated people and 0 to 9 among vaccinated people. It also shows the number of days it will take for the outbreak to peak, in this case, day 72.

But if that same 700-student elementary school got its vaccination rate up to 95% from the districtwide level of 83%, the chance of the one case becoming more than 10 cases drops to 4% and the likely outbreak size is from 10 to 23 unvaccinated people and 0 to 3 vaccinated people. The outbreak peaks on day 9.

Spreading the tool to other states

Once Meyers' team showed the tool to other researchers, more states wanted to be able to use the tool. "It really took off," she said.

Using state vaccination data spreadsheets, Meyers' team was able to make the tool available to any state that wants it or any state where the vaccination rate of schools is readily available. So far 22 states from Maine to Washington and Louisiana to Minnesota are using it.

"When individuals or community leaders can get that insight for themselves, they are using it to make informed decisions," Meyers said.

The measles calculator is housed on servers at the Texas Advanced Computing Center at UT. But any state that wants to have their own version on their state health website can do that. When Illinois wanted a measles calculator on its state health website and branded with that state's logo, the UT team happily gave them the computer code to do that.

"What we sparked in Austin really did benefit this whole outbreak," Meyers said.

What about other infectious diseases?

A similar calculator could be created for any vaccine-preventable disease, including mumps and rubella. The rate of spread would be different based on how infectious the disease is and the effectiveness of the vaccine, as well as the vaccination rates.

EpiEngage is also launching a local influenza forecasting hub that will allow cities to forecast the amount of flu in their area instead of by state. "It takes all projections and looks at them together," Meyers said. "What we saw personally is that what happened at a state level may not be what's happening in Austin or Dallas or El Paso."

Respiratory viruses like flu, COVID-19 and RSV (respiratory syncytial virus) will remain a threat every year.

Meyers also worries about outbreaks of mosquito-borne illnesses such as zika, West Nile, dengue fever, malaria and chikungunya. Climate change has changed where mosquitoes are living, making these diseases more of a threat in Texas.