The United States has more than 18,000 confirmed cases of coronavirus, including 227 deaths and 147 recovered, according to Johns Hopkins University.

A staffer in the office of US Vice President Mike Pence has been infected with the novel coronavirus disease, according to Pence's press secretary Katie Miller.

She noted that the staffer has not been in contact either with Pence or President Donald Trump, but did not specify his identity.  

Both Trump and Pence earlier tested negative for the virus. Trump underwent testing after concerns emerged regarding his close contact with people who ended up contracting the disease.

The development marks the first known COVID-19 positive test for a White House staffer. Earlier, two US lawmakers also said they had contracted the disease.

Due to the outbreak, the US has stepped up measures to combat the spread of coronavirus, including banning all flights to and from a number of countries, including Mexico, the European Union, and China, where the virus originated last December.