People get sick, especially in autumn. And they infect each other. Reporting that some people working at the lab were sick, without any knowledge about kind of sickness is only going to add fuel to the conspiracy theories.
The workers at the lab "were tested and there was no evidence found of Covid antibodies."
https://www.cnn.com/2021/05/23/politics/us-intelligence-repo...
So theoretically it's possible that three workers at the lab were sick -- and hospitalized -- but with, say the seasonal flu. The original reports from the State Department about this even specified that the workers had been sick with symptoms "consistent with both COVID-19 and common seasonal illness."
https://www.marketwatch.com/story/new-report-of-illnesses-at...
Tested by whom and how? If a trustworthy disinterested party positively identified the workers, took their blood samples, and tested them via a procedure with a low false-negative rate, then the test results are meaningful. Otherwise, there is reason for doubt.