The number of confirmed cases in Clark County increased from 350 to 443 overnight, while the state reported an increase from 420 to 535 late Thursday

This undated electron microscope image made available by the U.S. National Institutes of Health in February 2020 shows the Novel Coronavirus SARS-CoV-2. Also known as 2019-nCoV, the virus causes COVID-19. The sample was isolated from a patient in the U.S. (NIAID-RML via AP)

The number of confirmed COVID-19 cases in both Clark County and the state of Nevada registered its sharpest one-day increases since the first two cases were reported in the state March 5.

The Southern Nevada Health District reported Friday morning that the number of confirmed cases in Clark County had increased from 350 to 443 overnight.

“As testing capacity increases, we know we’ll see our (case) numbers grow,” Mike Johnson, director of the district’s community health division, said during a morning telebriefing for reporters.

Of the reported Clark County cases, 80 people, or about 18 percent, have required hospitalization, a figure that excludes the 10 cases that resulted in death. Of those hospitalized, 20 percent were in intensive care units, with nearly 14 percent on ventilators to assist them with breathing, according to new information provided on the district’s website.

Of those hospitalized, 29 people, or 36 percent, had underlying health conditions, such as heart disease, diabetes, high blood-pressure, a compromised immune system, chronic kidney disease or chronic lung disease.

Such underlying medical conditions put a person at “higher risk for complications from COVID-19,” district spokeswoman Jennifer Sizemore wrote in an email.

“Diabetes, even when well managed, can make a person’s immune system less able to fight off infections,” she said. “Other chronic conditions, even when well managed, impact a person’s overall health.”

During the telebriefing, the district said that it had only 119 test kits remaining with which to test people for the new coronavirus and that it currently can test about 40 people per day.

However, testing by private labs is on the upswing, including testing of individuals with milder symptoms. Anecdotal evidence suggests that testing had been limited primarily to individuals with more severe symptoms or those who were part of disease-transmission investigations.

“What we’re seeing on the front end is a lot more urgent care and drive-by testing coming through,” said Kimberly Hertin, disease surveillance supervisor for the district.

Testing also continues at a public lab in Reno.

Meanwhile, the number of confirmed COVID-19 cases in Nevada jumped from 420 to 535 late Thursday, and from 535 to 621 on Friday, according to state data posted late Friday.

The new total reported by the state Health and Human Services Department and posted on the nvhealthresponse.nv.gov website Friday night was derived from tests on 8,522 individuals. Seven percent of those tested were positive for the virus.

The death toll from the disease caused by the new coronavirus held steady at 10, all of which have occurred in Clark County.

Elsewhere in the state:

■ The Washoe County Health District reported eight additional cases of COVID-19, increasing the total there to 75. It also reported that a fifth Washoe County resident had recovered and was released from self-isolation.

■ A third case was reported in Elko County. The individual was self-isolating at home.

■ Carson City Health and Human Services reported one new positive case of COVID-19 in the Quad County region of Carson City, Douglas, Lyon and Storey counties, bringing the total number of cases there to nine.

The new case involves a Douglas County woman in her 70s with a history of recent travel. She is self-isolating at home.

After Clark County, Washoe County has seen the second-highest total of cases. Cases also have been reported in Carson City and Douglas, Elko, Lyon and Nye counties.

Contact Mary Hynes at mhynes @reviewjournal.com or 702-383-0336. Follow @MaryHynes1 on Twitter.