(Adds some cases tied to nursing home; background)
March 3 (Reuters) - The number of coronavirus cases diagnosed in Washington state rose on Tuesday to 27, including nine deaths, up from 18 cases and six deaths a day earlier, state health authorities reported, in the largest U.S. outbreak to emerge from local transmission.
The deaths - eight in King County and one in neighboring Snohomish County - mark the first fatalities documented in the United States from a respiratory illness that has killed more than 3,000 people worldwide, mostly in China, where the epidemic originated in December.
All 27 confirmed cases in Washington are clustered in two adjacent Puget Sound counties in the greater Seattle area, making it the largest concentration detected to date by the U.S. public health system.
Several of those who died had been residents of a long-term nursing care facility in the Seattle suburb of Kirkland called LifeCare, according to information furnished by the Seattle & King County Public Health agency.
The U.S. Centers for Disease Control and Prevention (CDC) lists 108 confirmed and presumed cases of coronavirus in at least a dozen states, nearly half of them patients who were repatriated from the Diamond Princess cruise liner that had been quarantined in Japan. (Reporting by Steve Gorman; Editing by Sandra Maler and Jonathan Oatis)