Are Trump's rallies spreading coronavirus?

Stanford University economists estimate that President Donald Trump's campaign rallies have resulted in 30,000 additional confirmed cases of COVID-19, and likely led to more than 700 deaths overall, according to a paper posted online this weekend.

Lisa Bernhard produced this report.

Stanford University economists estimate that President Donald Trump's campaign rallies have resulted in 30,000 additional confirmed cases of COVID-19, and likely led to more than 700 deaths overall, according to a paper posted online over the weekend.

The research analyzed data following 18 Trump rallies held between June 20 and Sept.

22, three of which were indoors.

In recent months, Trump has held several dozen rallies in states such as Pennsylvania, Minnesota and Wisconsin, where coronavirus infection rates were already on the rise.

Many among the packed crowds were not wearing masks, creating a risk of spreading the virus as they cheered their candidate on.

An infectious disease expert at Johns Hopkins Center for Health Security told Reuters, the Stanford paper was "suggestive" of spread from the events, but not definitive because it was not based on an investigation of actual cases.

Minnesota public health officials have attributed four COVID-19 outbreaks and more than 25 cases to Trump rallies held in the state in September and October.

An additional 11 state health departments contacted by Reuters said they had not been able to trace infections to the rallies, although some, including Michigan and Wisconsin, have determined that individual people who later tested positive for COVID-19 were present at Trump campaign events.

Disease experts say that rigorous contact tracing from one such large event could help arrive at an accurate prediction of how infectious such rallies can be.

But the United States has fallen behind other developed countries in this regard, due to a lack of funding and coordination for contact tracing by the Trump administration.