WASHINGTON - Nursing homes across the United States are becoming the latest hot spots for Covid-19 infections, with outbreaks in long-term care facilities and retirement communities reported in several states in recent days.

The coronavirus raced through the Pleasant View Nursing Home in Maryland, infecting 77 of its 95 residents, or a whopping 81 per cent, and killing five of them in as many days.

Local health officials said that all five had underlying medical conditions, and ranged in age from being in their 60s to their 90s.

Over in Tennessee, two residents of the Gallatin Centre for Rehabilitation and Healing died as more than 100 of its residents and staff members tested positive for Covid-19, the disease caused by the coronavirus.

The outbreak prompted the evacuation of the remaining residents elsewhere as the 204-bed nursing home underwent deep cleaning.

Nearly 15 per cent of New York's 1,200 Covid-19 related deaths were nursing home residents as of Monday, according to a spokesman for the state's health department. More than 1,000 confirmed cases have been reported in 155 nursing homes across the state.

"This virus preys on the vulnerable. It preys on seniors, it preys on people with compromised immune systems and underlying illnesses, and coronavirus in a nursing home can be like fire through dry grass," said New York Governor Andrew Cuomo.

The number of confirmed cases in the US surged on Tuesday (March 31) to 189,000, making up a fifth of the world's cases.

Some 147 nursing homes in 27 of America's 50 states had at least one resident diagnosed with Covid-19 as of March 23, according to the Centres for Medicare and Medicaid Services (CMS). It has not released updated figures since then.

"Although 147 is a small fraction of the over 15,000 nursing homes across the country, given the disproportionate effect on our nation's older population, this is a cause for concern," said the CMS in a statement announcing its findings from an inspection of America's first coronavirus cluster - the Life Care Centre nursing home in Kirkland, Washington.

Experts have warned of the potential for the virus to spread within these long-term care facilities, which house dozens of senior citizens in close quarters.

"Based on what we know now, those at high-risk for severe illness from Covid-19 are people aged 65 years and older, and people who live in a nursing home or long-term care facility," said the Centres for Disease Control and Prevention (CDC) on its website.

About 1.35 million people lived in nursing homes across America as of 2016, the most recent year for which national data from the National Centre for Health Statistics (NCHS) was available.

Of these, 84 per cent were aged 65 and older and almost all needed assistance in daily activities such as bathing, dressing, and going to the toilet.

Many also had underlying medical conditions that put them at risk for more severe illness from Covid-19. The NCHS reported that 32 per cent of nursing home residents had diabetes, 38 per cent had heart disease, and 72 per cent had high blood pressure or hypertension.

American researchers studying the Kirkland nursing home outbreak also found that the coronavirus could spread rapidly within a nursing home once it was introduced, even if many patients did not display symptoms and control measures like restricting visitors were carried out.

The lack of isolation of patients who did not display symptoms but later tested positive for the coronavirus likely contributed to the rapid spread of the virus, they found in a CDC report published on March 27.

To protect residents, senior facilities have stopped community activities, limited visitors to essential staff and visitors, and implemented infection control measures like wiping down commonly used surfaces more frequently.

Nursing home residents who test positive for the coronavirus have been sent to nearby hospitals, and the National Guard has also been deployed to help overwhelmed nursing homes cope with outbreaks.

Their assistance ranges from helping to test residents for the coronavirus in West Virginia and Tennessee, to assessing residents' medical conditions in Maryland and cleaning facilities and training staff in Georgia.

"Georgia's top priority is increasing healthcare capacity to protect vulnerable Georgians, especially those residing in long-term care facilities," said Georgia Governor Brian Kemp in a statement on Tuesday announcing the deployment of more than 100 guardsmen to long-term care facilities in the state.

"If we can keep these populations as healthy as possible, we will be able to conserve precious medical supplies and hospital bed space in the coming days and weeks."