TORONTO -- Nearly one month after Ontario's long-term care sector recorded its first COVID-19 death, the province will begin "proactive surveillance testing" all residents and staff to gain a better understanding of how "pervasive" the virus is in the province's nursing homes.

Public Health units are being asked by the Ministry of Health to develop a plan that would see all residents and staff in the province's 630 long-term care homes tested for the disease –with a particular focus being placed on asymptomatic staff who might unintentionally introduce the virus into a home.

Ontario's long-term care homes have been hardest hit by the spread of COVID-19 claiming the lives of 400 people, including 399 residents and one health-care worker, and leaving thousands more infected with the virus.

The government introduced new measures designed to limit the spread, including restricting nurses and personal support workers from being employed at more than one long-term care home for two weeks, re-deploying hospital staff and resources to affected homes and creating pandemic plans for homes that have yet to experience an outbreak.

However, the government's approach to testing has been criticized as being too limited in scope –the province said only those who have come in contact with a confirmed COVID-19 carrier would be tested for the virus.

According to the Ministry of Long-Term Care roughly 10,000 staff and residents have been tested for the virus –10 per cent of the total number of people living and working in the facilities – including 3,000 people over the weekend alone.

In a memo to local public health officials on April 21, Ontario's Deputy Minister of Health Helen Angus acknowledged that the only way to "understand the current status of COVID-19" in an individual home is to screen asymptomatic residents for the virus.

"Testing is an important component of a comprehensive response plan being implemented to address COVID-19 in this vulnerable population in order to ensure that these facilities have every resource needed to stop the spread of COVID-19," Angus said in the memo.

Public health units are being told to prioritize homes that are experiencing outbreaks before moving to residences with no symptomatic residents or staff and can lean on local paramedic services to help increase their testing capabilities.

"This point-in-time testing will enable homes, PHUs, and the province to better understand the prevalence of COVID-19 in long-term care homes and inform future planning," Angus said in the memo.

"When they were released, we had every expectation that local public health officials would apply this discretion liberally out of an abundance of caution, including proactively testing all residents and staff if necessary," the statement reads. "The significant increase in daily testing since their release confirms that many public health units and long-term care homes experiencing an outbreak, defined as only one case, have tested proactively and broadly."

The ministry says details and timeline for implementation has yet to be shared with public health units.

Earlier this week the province conceded that the outbreaks in Ontario's long-term care homes now makes it difficult to predict the overall number of lives COVID-19 could ultimately take.