Public health officials have confirmed the first U.S. case of a mysterious coronavirus that has already killed at least 6 people and sickened hundreds of others in China, according to two reports.

A White House spokesman declined to comment, referring calls to the Centers for Disease Control and Prevention. The CDC did not immediately respond to CNBC’s inquiries about the report. 

A traveler from China has been diagnosed in Seattle with the Wuhan coronavirus, according to Reuters, citing a CDC spokesperson. The CDC is expected to make the announcement at a media briefing scheduled for this afternoon, CNN reported.

Public health officials have confirmed more than 300 cases of the illness, which has evoked memories of the 2003 outbreak of severe acute respiratory syndrome, or SARS, in China. Health officials have also confirmed cases in Thailand, South Korea, Japan and Taiwan.

The World Health Organization is expected Wednesday to convene a panel of experts in Geneva, Switzerland, to consider whether the illness should be a global health emergency.

The last time WHO declared a global health emergency was in 2019 for the Ebola outbreak in eastern Congo that has killed more than 2,000 people. The agency also declared global emergencies for the 2016 Zika virus, the 2009 H1N1 swine flu and the 2014 polio and Ebola outbreaks.

Chinese authorities say many of the patients with the new illness had come into contact with seafood markets, suggesting the virus is spreading from animals to people. However, health officials say some “limited human-to-human transmission” occurred between close contacts.

In addition to the health concerns, some experts worried about the economic consequences if coronavirus evolves into a pandemic. They pointed to the fallout from the deadly SARS crisis in 2003. SARS, which emerged in China in 2002 and was identified in 2003, killed nearly 800 people worldwide. It hit Asian cities such as Hong Kong, Singapore, Taipei and Beijing the hardest and triggered a severe downturn in the region.

People can protect themselves from the virus by washing their hands with soap and water, avoid touching eyes, nose or mouth and keeping away from sick people, according to the CDC. Many people in China have purchased face masks to protect themselves from the outbreak.

—CNBC’s Weizhen Tan contributed to this report.

This is a developing story. Please check back for updates.