The Centers for Disease Control and Prevention (CDC) has reported two new cases of the coronavirus that do not appear to be travel-related, bringing the total number of suspected cases with unknown origins to four.

One case was reported in Oregon and the other in Washington state, the CDC announced late Friday. The new untraceable cases follow California health officials on Friday reporting a second case of coronavirus in a person who had no previous connection to anyone with the disease.

The cases have raised concerns among health officials about so-called community spread, in which an illness spreads in communities despite the source of the infection being unknown. The first suspected case of community spread was announced in California on Wednesday.

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More than 60 cases of coronavirus have been confirmed in the U.S., with the majority coming from Americans repatriated from the Diamond Princess cruise ship that was quarantined in Japan.

Before the four Western cases announced this week, state health officials and the CDC were able to trace the origins of coronavirus cases.

"I understand this may be concerning to hear, but this is what we have been preparing for," said Sara Cody, the health officer in Santa Clara County, Calif., where one of the cases was confirmed Friday.

"Now we need to start taking additional actions to slow down the spread of the disease," she continued.

The county health official said the second such case in California signals "that it’s now time to shift how we respond to the novel coronavirus."

"The public health measures we’ve taken so far, isolation, quarantine, contact tracing and travel restrictions have helped to slow the spread of disease ... but now we need to add other public health tools to the mix," she added.

On Friday, the World Health Organization raised its coronavirus risk assessment to "very high" but said that the outbreak has yet to become a global pandemic.

There are more than 85,000 reported cases of the virus worldwide and almost 3,000 deaths — the vast majority in mainland China, where the outbreak originated.