The US Centers for Disease Control and Prevention has listed 241 patients under investigation for the novel coronavirus in 36 states, according to an update posted to the agency's website Friday.

Of them, six have tested positive, 114 negative, and 121 are still pending.

There is one case is in Arizona, one in Washington state, two in California and two in Illinois.

The sixth patient is also the first confirmed case of person-to-person transmission of the virus in the US, according to an announcement by the CDC on Thursday. He is the husband of an Illinois woman who was diagnosed with the virus after returning from Wuhan, China, where the outbreak originated -- though he did not travel to China himself.

Pending cases includes specimens that have been received and not yet undergone testing, as well as those in transit to CDC from health authorities in various states.

Previously, there were 165 patients under investigation in 36 states, as of January 29, including five positive, 68 negative and 92 pending cases.

CDC is the only lab in the US that can conduct diagnostic testing for the virus, but it is developing coronavirus testing kits to share with "domestic and international partners," according to an earlier statement.