Partly Cloudy With A 75 Percent Chance Of COVID Exposure

It’s 6:30 a.m. and your third alarm is blaring. Another 10 minutes and you’ll have to miss breakfast before going to work. You get up, brush your teeth, shower and start a pot of coffee while watching the morning news. After the station’s meteorologist tells you it’s sunny with a high of 70 degrees, a health reporter follows up with the COVID-19 forecast: red-alert level today, with a 75 percent chance of exposure in spaces with at least 50 people.

You respond to the risk by taking a rapid test before leaving the house — snapping a picture of the negative result for your colleagues — and grabbing your N95 mask.

This is a hypothetical future, but one that a new team at the Centers for Disease Control and Prevention is working on. The Center for Forecasting and Outbreak Analytics got an initial $200 million in funding from the American Rescue Plan to recruit data scientists, epidemiologists and science communicators who will come up with forecasts for the public and promote data-based decision-making. CFA aims to operate “like the National Weather Service, but for infectious diseases,” said epidemiologist Caitlin Rivers, the new center’s associate director for science, in an April article in The Washington Post.

Which would be great — except that the forecasts have less data to work with now than they’ve had in years. COVID-19 case data is less and less reliable thanks to rapid testing, for one. In addition, hospitalization data can lag behind trends in transmission and may become unavailable in the coming months. And new sources like wastewater surveillance aren’t yet ready to replace clinical data. Imagine producing a weather forecast without reliable temperature or humidity measurements.

Two converging trends are causing case data to become less useful. First, more Americans are using at-home rapid tests, and second, fewer Americans are using lab-based PCR tests.

About six times as many at-home tests as PCR tests are being taken in the U.S., according to Mara Aspinall, a diagnostic-testing expert and health-care industry consultant. Using data from test manufacturers and retailers, Aspinall has kept a close eye on test capacity in the U.S. throughout the pandemic, and at this time last year, Americans were taking considerably more PCR tests than at-home tests.

Unlike PCR test results, which are automatically reported by the labs that process the tests, the vast majority of at-home test results are not reported to public-health authorities. In recent months, PCR tests have also become less available. States such as Vermont and Colorado are shutting down free public-testing sites and directing patients to at-home tests and private health-care providers instead — even as government funding to cover tests for uninsured people has run out.

“The official numbers we hear about on a daily basis, in terms of official COVID-19 cases, is becoming an increased undercount of the true number of…