ELLSWORTH — The number of confirmed cases of coronavirus in Hancock County rose to five this week as Governor Janet Mills extended a state of civil emergency through May 15, enabling her to continue using executive powers to respond to the pandemic.

Statewide, the Maine Center for Disease Control and Prevention (CDC) had confirmed 734 cases as of early Wednesday morning and 20 deaths.

Most of the cases are concentrated in Cumberland and York counties, although community transmission has been confirmed in Penobscot County, which had 34 cases as of Wednesday morning. Officials also are monitoring several outbreaks at long-term care facilities around the state, including at the Tall Pines Retirement and Health Care Community in Belfast.

Following federal guidelines, nonresidents who test positive while in Maine are counted in their home state of residence. Last week, Dr. Nirav Shah, director of the Maine CDC, reported that 13 Maine residents have tested positive out of state and 17 nonresidents have tested positive while in Maine. The CDC has not provided any more information on those cases, such as the county in which they are located.

Officials said it’s difficult to predict when the state will hit its peak in terms of cases, and many expect there to be waves of infections until a vaccine is widely available.

Massive worldwide efforts are underway to create a vaccine, but one that is fully tested will take at least one to two years, and would be first distributed to those at highest risk of exposure or severe disease, according to the Maine CDC.

“There are many predictive models out there, some that actually say that the surge will hit us as early as next week and some that put it as far out as June and July,” said Dr. James Jarvis, who is part of the Northern Light Health team leading the response to the virus, in a call with reporters on Friday. “We tend to follow the one that the state is using and that would put us somewhere around the 14th to the 21st of April.”

Shah said on Tuesday that the peak of cases is generally evident only “in retrospect.”

“The reason we do modeling,” said Shah, “is not to predict when we might be at the peak but to plan for what resources we might need, whenever that peak happens, whatever it might look like.”

Shah has repeatedly stressed that the number of confirmed cases is “only the tip of the iceberg,” and that without large-scale testing, residents must assume the virus is everywhere.

Expanding testing capacity is also key, Governor Janet Mills said Tuesday, in making a decision on when to lift the stay-healthy-at-home order, now in place until April 30.

“The more test kits we get the better able we will be to allow more people to go back to work in different areas,” Mills said.

“The numbers that Dr. Shah presents every day — when we say it’s new cases, it’s really new test results as opposed to new cases,” she said later. “The cases are out there, we just haven’t documented them, confirmed all of them. It is everywhere; we have to assume it is everywhere.”

Northern Light Health has been conducting tests in-house for several weeks and is currently able to test between 850 and 1,000 people each week, said Jarvis. So far, the hospital system has tested 2,778 people, 79 of whom have tested positive, said Kelley Columber, director of communications for Northern Light Maine Coast and Blue Hill hospitals, in an email.

“Any given day we are testing somewhere between 100 and 150 individuals,” said Jarvis, “Many of them health-care workers because they are part of the Tier 1 category.”

Northern Light has largely limited testing to “Tier 1” patients, defined by the federal CDC as “hospitalized patients and symptomatic health-care workers,” to conserve limited resources, said Jarvis.

Certain chemicals necessary to process the tests have been in short supply nationwide, and the hospital system only has so many personnel available to run the tests.

“It’s important that we continue to conserve testing until testing is more readily available, which we all hope happens soon,” said Jarvis.

On the state level, Shah has said that the state does not have a backlog of tests waiting to be processed and that whether or not someone is tested is a decision made in consultation with his or her health-care provider.

Testing health care workers and in-patients also helps prolong the supply of personal protective equipment, since workers do not need to wear as much gear to care for patients who test negative.

Health-care workers contracting the virus has been of particular concern to officials, as it could quickly strain the system if they are quarantined and out of work.

Statewide, 110 health-care workers had tested positive for the virus as of Monday, Shah said in his daily briefing, accounting for roughly 16 percent of the then-698 confirmed cases. (The state defines health-care worker in very broad terms, including anyone who might come into contact with a patient, such as janitorial and other staff.)

Those figures of infected health-care workers are similar to what has been seen in Spain, one of the countries in Europe hardest hit by the virus. Roughly 14 percent of the country’s confirmed cases in late March were among health-care workers, according to National Public Radio.

Jarvis has said in past briefings that Northern Light feels it has adequate personal protective equipment for employees, at least for the time being, but said that “Some of them we feel did contract the virus in contact with patients; most of them, however, have been through community spread, and we have a very good contact tracing.”

Jarvis said all Northern Light Health staff are required to wear a mask “if we feel they’re going to be within 6 feet of another individual,” and that all employees have been provided with procedural masks.

Northern Light is not yet cleaning and reusing masks, said Jarvis, “But we do have a procedure to do that that has been validated by the government.”

Jarvis added that “The risk, however, for health-care providers is high when you’re face to face with individuals who are positive for COVID-19.”

So far in Maine, 292 residents have recovered from the virus and 124 have been hospitalized at some point during their illness. The Maine CDC is no longer reporting the number of negative tests because outside labs testing samples from Maine makes getting an accurate figure difficult, according to the CDC website.

Shah also noted on Tuesday that 37 people with COVID-19 were in regular hospital beds while 21 were being treated in intensive care units. Nine of those being treated were on ventilators.