Reaching 90% of contacts, for instance, will be especially difficult in states and regions still grappling with lots of new infections. Take Massachusetts, which put to work a 1,000-person contact tracing task force at the beginning of the month. But new confirmed cases in the state are still generally exceeding 1,000 daily, and nearly reached 1,700 on Thursday, so every tracer on the team will need to track down and convince some multiple of that number to stay away from others every day. While shelter-in-place rules are in effect, that multiple may be only two or three people. But as regions relax social distancing measures, the average number of contacts for infected patients could rise to closer to 20.

NPR reported that 44 states and the District of Columbia now plan to bolster their contact tracing teams, collectively increasing them from about 11,000 today to more than 66,000 in the weeks ahead.

But that’s likely not going to be enough. The National Association of County & City Health Officials estimates that US tracing efforts will require 30 professionals for every 100,000 people (or more than 98,000 people nationwide).

Only seven states have plans that would reach that target, including California, New York, and Illinois, NPR found. Only one, North Dakota, meets it currently.