US health officials reported on Friday a fourth case of a novel coronavirus of unknown origin, indicating that the disease is spreading across the country.
The most recent case is a boy under the age of 18 in Washington State who tested "presumably positive", local authorities said without disclosing further details about the patient.
He is currently in domestic isolation in Snohomish County. The high school he attends will be closed until March 3 while being cleaned thoroughly, the Washington State Department of Health said.
In neighboring Oregon, the authorities announced on Friday that an adult who had contact with people at a primary school had been hospitalized and was also classified as "presumably positive".
A positive test is treated as "suspected" until the results are confirmed by the Centers for Disease Control and Prevention.
"We expected and were prepared for it," Patrick Allen, director of the Oregon Health Department, told reporters.
The school will be closed until March 4th as it undergoes a thorough cleaning. The officials said they would speak to employees and parents.
Earlier on Friday, California health officials said an older woman with an unknown origin was infected – the second such case in the northern part of the state.
"This new case indicates that there is evidence of community transmission, but the extent is not yet clear," said Sara Cody, director of public health in Santa Clara County.
"What we now know is that the virus is here and at some level, but we still don't know to what extent," she added.
The two cases in California are near Silicon Valley, where technology giants like Apple, Google and Tesla are based.
The recent infections have increased fear of an outbreak across the country.
However, President Donald Trump downplayed US risk at a campaign rally in South Carolina, accusing Democrats and the press of fueling hysteria.
"We are preparing for the worst," he said. "My government has taken the most aggressive measures in modern history to prevent the spread of this disease in the United States."
He called the corona virus the "new joke" of the Democrats.
"The Democrats politicize the corona virus. They politicize it," he said. "You have no idea. You can't even count your votes in Iowa."
According to the Centers for Disease Control, more than 60 people in the US are infected with the disease, most of them in California.
State governor Gavin Newsom said Thursday that 33 people had tested positive for the virus, and five of them had left California.
Worldwide, more than 85,000 people are infected and over 2,900 have died.
The escalating number of cases has brought stock markets to collapse and increased fears that the disease could destroy the global economy.
(Except for the headline, this story was not edited by NDTV staff and published from a syndicated feed.)