# This calculator estimates your risk of contracting Covid-19 | Innovation

As the Covid-19 Delta variant changes what we consider to be “safe” and “dangerous” activities, a new online tool called the microCOVID project attempts to quantify these evolving risks. The model evaluates a given scenario – say, a vaccinated person eating at a covered restaurant with friends – in a specified county in the United States and produces an estimated risk of contracting Covid-19.

“It gives you a kind of common playing field to understand all kinds of activities,” says Ben Shaya, contributor to the microCOVID project. “It separates some of the emotional charge from it.”

The project began after Shaya’s “pandemic group” of friends and roommates wanted to be fairer about safety precautions, so they took a science-based approach to their decision-making. “They wanted to have a better way of being fair about what people could do,” he says.

The group of friends created a mathematical model that draws on the latest research on masks, vaccine effectiveness, current cases in each county and more, before translating it into a numerical value. They kicked off the project in May 2020 for their own use and, within months, created a version for the public. The site includes two tools: one calculator, and one risk monitoring. The Calculator is designed to give users an idea of ​​the risk of a single event or scenario, while Risk Tracking counts a person’s activities to create an overall risk score that can be shared with others. others. The team that started with a handful of friends incorporated dozens of volunteer collaborators over the next few months, including mathematicians, data scientists and a primary care clinician.

The group decided to measure the risk in a unit they named microCOVID: a one in a million chance of being infected with Covid-19. The website by default budgets 10,000 microCOVIDs per person per year, which equates to a 1% chance of contracting the virus, according to the site.

To use the calculator, users select different scenarios, such as attending a crowded party or meeting a friend for dinner, and enter details about the mask they are wearing, whether they are fully immunized, whether they are away. ‘inside or outside. The estimate jumps between the color coded risk scales. For example, a fully vaccinated person in Manhattan wearing an N95 mask could have a risk of around 4 microCOVIDs if they went shopping for an hour. In the model’s default budget of 200 microCOVIDs per week, this is considered a “low risk” activity. Another Manhattanite in the same scenario, but unvaccinated and unmasked, would have a risk closer to 80 microCOVID, or nearly half of the weekly allowance.

Users can also create a personalized scenario, such as attending an outdoor wedding in Miami. Let’s say the person is not vaccinated and there will be about 100 guests of varying immunization status. Because people will eat and drink, no one will be wearing a mask, and people will likely be separated from normal social distancing for about five hours. In this scenario, the risk to the user is approximately 3,000 microCOVID, or “dangerously high risk”. If all other factors remain the same, but that person is fully immunized, their estimated risk of infection drops to a “very high risk” of 500 microCOVID.

The site’s monitoring and risk calculator is adaptable, so people can change the budget based on their concerns and the vulnerabilities of those around them. “No one thinks he’s dangerous,” says Jenny Wong, a collaborator on the microCOVID project. “Attention means different things with different people. The risk monitoring, which was the original form of the project, works more like a financial budget, Wong explains. She may avoid eating out, for example, if she wants to see a friend the following week. That way, she says, “people can save for the things that matter to them.”

“The way we posed the pandemic is that any business outside of your home is very risky, and everything inside is fine. And that is of course not exactly how life works ”, says Monique Gandhi, an infectious disease physician at the University of California at San Francisco, who is not involved in the project. Gandhi uses similar risk calculators in his work to assess patients’ risk of contracting various diseases and illnesses. She appreciates the user-friendly interface and explanations of the site, so that people can understand the factors that influence their risk estimates.

Associating a number with a risk can be helpful in making decisions that involve uncertainty and fear. “That tells you okay, how do you directly compare eating in a restaurant to sitting on a plane for three hours? ” she says. To update the calculator and risk tracking to account for the Delta variant, the team incorporated the latest data on transmission rates and number of cases. When the model was updated to include the more transferable Delta variant, Wong noticed that activities deemed low risk a few months ago are now moderate or high risk. “I went from ‘I can do this once a week’ to an activity maybe once every two months. ”

Being within a certain range of the risk budget may seem like guaranteed safety, but that doesn’t mean your risk of infection is zero, warns F. Perry Wilson, an epidemiologist at Yale University, who is not involved in the project. Risk budgeting tools like this can also give “a false sense of security,” he says, and “could give people some sort of permission to behave in a way that could put them more at risk than they are. ‘they don’t appreciate it “.

Wilson is concerned about the potentially wide margins of error and says he’s hesitant to put too much stock in a single issue. Nonetheless, Wilson suggests using the tool to get a rough idea of ​​your risk, while remembering that the studies and data the calculator is based on are still early and change often. The site White paper describes specific peer-reviewed studies, contract tracing data and aerosol models used in the calculator, which are updated as new research emerges.

As more heritable variants like Delta become dominant, Gandhi says these risk analysis tools can become particularly appealing to the public. “I think it was, in a way, the most difficult time of the pandemic because there was this glimpse of normalcy,” Gandhi said, referring to the spring of this year. Some activities considered safe in May were deemed too risky in August. She says customizable assessment tools like the microCOVID project can empower those who are frustrated with unique advice. “Everyone has their own risk tolerance, and it may not be someone else’s risk tolerance,” says Gandhi.

The microCOVID project is one of several Covid-19 risk assessment tools aimed at helping the public make evidence-based decisions about their health. Mathematical 19 years old and me The calculator is a credit score style tool that allows users to enter their location, age, health issues, and behaviors before producing a score that reflects the risk of infection. Another free tool is MyCOVIDRisk, a questionnaire-based web application that assesses the risk level of a given scenario.

Although the team updates the microCOVID project model as new data emerges, they admit that it’s difficult to stay on top of the evolving information. Wong recommends that users check the calculator frequently to get the best assessment of their risk of infection, as the number of local cases can change quickly. Other parts of the model require regular adjustments to keep the estimates as accurate as possible. The team updated the underreporting factor, which takes into account cases that are not on the official case tally, three times since the start of the pandemic. Currently, the calculator multiplies the number of cases by a factor of 6, assuming there are many more infected people in the area who are not being tested – something, Wilson said, might have been correct at the start of the test. pandemic, but is probably an overestimate now. While there is a “fuzziness” in the final estimate, Wong says, it does provide a framework for understanding risk.

Despite some shortcomings, Wilson believes the calculator is particularly useful for identifying specific changes that may reduce your risk of contracting Covid-19, such as adding a properly fitted mask or going outdoors. “What I found fun and informative about it was seeing how my risk goes up and down under various scenarios,” says Wilson. “Those little clues, the active things you can do [to reduce the risk of infection] I think they’re super helpful and, and I’m glad they’re there for people to experience.