US sues Texas to block state troopers from stopping migrants

From the article: "(t)he(sic) Biden administration sued Texas on Friday, July 30, 2021 to prevent state troopers from stopping vehicles carrying migrants on grounds that they may spread COVID-19, warning that the practice would exacerbate problems amid high levels of crossings on the state's border with Mexico."

I do not understand this. How does stopping the vehicles exacerbate the spread of COVID? Wouldn't infected people moving around be more of a factor in spreading the virus, rather than stopping them?