Heart disease is the most common underlying health condition in coronavirus patients admitted to intensive care units in hospitals across the country, it emerged yesterday.
An analysis of the first 327 of the sickest patients with the virus revealed that half had chronic heart disease.
Chronic respiratory disease was diagnosed in 76 patients and 74 had diabetes.
Fifty-three were obese and 34 had asthma.
Thirty-one suffered from cancer and 20 had chronic kidney disease.
Underlying illness is known to put people at higher risk of complications.
It was the first time Chief Medical Officer Dr Tony Holohan had provided an insight into the type of conditions those who are hardest hit by the infection suffered from.
He said that in some cases there was overlap where a patient could have suffered from more than one underlying condition.
Dr Holohan warned that if today was May 18, the country would still not be ready to enter phase one of post-lockdown. However, he remains hopeful.
An additional 37 deaths from the virus were announced yesterday, bringing the toll to 1,375.
There were 265 newly diagnosed cases of the virus, pushing the total to 22,248.
Dr Holohan said there is a persistently high volume of newly-infected people emerging from the community, many of them young .
The number of patients in intensive care has dropped to 86, but an additional 196 residents or staff in long-term facilities have tested positive, including 160 in nursing homes, which have also seen nine more clusters.
Commenting on the decision to expand testing to the wider population who have at least one potential symptom, Dr Holohan said he expects it will be able to pick up any area of concern about infection outbreaks in the coming weeks.
He did not think it will over-burden the system, and there were moves under way to shorten the various stages involved before a patient gets their result.
It may be possible to provide the results to the patient directly from the lab, he added.
Quickly tracking contacts of a person who tests positive is vital to stop them infecting others and creating a new chain of transmission.
Asked about people who are cocooning and have been advised they can take a walk from this week, Dr Holohan said they will continue to be subjected to greater restrictions as the country passes through various phases out of lockdown.
"The safest thing is to stay at home, and if they take brief exercise they should not visit shops, handle surfaces or contact people and they should wash their hands when they come home," he said.
Questioned on whether patients who have not tested positive for the virus are being placed in wards with infected patients, he said there are clear procedures in place to separate both.
He refused to comment on the case of a deceased patient to whom this is alleged to have happened.
"The arrangements put in place would be to try to minimise the risk of infection," he said.
"This is a very transmissible virus. It is still possible where provision is made to limit the spread of the virus and a separate stream has been created that an infection with Covid-19 can arise in a non-Covid area."
Dr Holohan said the arrangements in relation to acute hospital care are "ones they can have confidence in". People with non-Covid illnesses should continue to present to hospital.
The HSE has urged people with non-Covid illnesses to continue to seek hospital care.
Its National Cancer Control Programme urged anyone with potential symptoms of cancer to telephone their GP to check them out.
The average number of cancers being referred weekly to hospital clinics has dropped to less than half of that before the announcement of Covid-19 public health measures.