The senior US scientist battling the coronavirus pandemic has been given extra security as he received threats after contradicting President Donald Trump's dubious interpretations and forecasts over the crisis.

The US Marshals service confirmed Thursday that Anthony Fauci, the widely-respected expert who is the public face of the government's response to the virus, was granted special security protection.

Fauci, a long-serving government official, stands at Trump's side at the daily televised White House briefings on the COVID-19 outbreak.  He has won a reputation for giving unvarnished and fact-based information about the pandemic, which has already killed 5,100 Americans.

The 79-year old doctor, the country's foremost expert on infectious disease, has been attacked by conservatives after pushing back against Trump's assertions about the virus.

He disagreed publicly with Trump's plan -- now dropped -- to ease quarantine restrictions by April 14, and has downplayed Trump's promotion of antimalarial drugs hydroxychloroquine and chloroquine as reliable treatment for coronavirus.

Trump supporters have strongly attacked Fauci online, accusing him of being an agent of the "deep state" trying to undermine the president.

Fauci brushed off questions about his security early Thursday. "It's really kind of crazy. We try not to pay attention to that and just focus on the responsibility and the job that we have. That's the most important thing," he told CBS News.

The Department of Health and Human Services did not confirm the extra security, but a spokesperson said "Dr. Fauci is an integral part of the US government's response against COVID-19."