Throughout March, as the pandemic gained momentum in the United States, much of the preparations focused on the breathing machines that were supposed to save everyone’s lives.

New York State Gov. Andrew Cuomo and President Donald Trump sparred over how many ventilators the state was short. DIYers brainstormed modifications to treat more patients. And ethicists agonized over how to allocate them fairly if we run out.

Now five weeks into the crisis, a paper published in the journal JAMA about New York State’s largest health system suggests a reality that confounds early expectations like so much else about the novel coronavirus.

Researchers found that 20 per cent of all those hospitalised died – a finding that’s similar to the percentage who perish in normal times among those who are admitted for respiratory distress.

But the numbers diverge more for the critically ill put on ventilators. Eighty-eight per cent of the 320 Covid-19 patients on ventilators who were tracked in the study died. That compares with the roughly 80 per cent of patients who died on ventilators before the pandemic, according to previous studies – and with the roughly 50 per cent death rate some critical care doctors had optimistically hoped when the first cases were diagnosed.

“For those who have a severe enough course to require hospitalisation through the emergency department it is a sad number,” said Karina Davidson, the study’s lead author and a professor at the Feinstein Institutes for Medical Research at Northwell.

The analysis is the largest and most comprehensive look at outcomes in the United States to be published so far. Researchers looked at the electronic medical records of 5,700 patients infected with Covid-19 between 1 March and 4 April who were treated at Northwell Health’s 12 hospitals located in New York City, Long Island, and Westchester County – all epicentres of the outbreak. Sixty per cent were male, 40 per cent female and the average age was 63.

“It’s important to look to American data as we have different resources in our health care system and different demographics in our populations,” Davidson said.

Medical workers transport a patient outside of a special coronavirus intake area at Maimonides Medical Center in Brooklyn (Getty)

The paper also found that of those who died, 57 per cent had hypertension, 41 per cent were obese and 34 per cent had diabetes which is consistent with risk factors listed by the Centres for Disease for Control and Prevention. Noticeably absent from the top of the list was asthma. As doctors and researchers have learned more about Covid-19, the less it seems that asthma plays a dominant role in outcomes. In fact there are only nine patients with asthma hospitalised at Northwell for the virus.

One other surprising finding from the study was that 30 per cent of the patients sick enough to be admitted to the hospital did not have a fever. Fever is currently listed as the top symptom of Covid-19 by the CDC, and for weeks, many testing centres for the virus turned away patients if they did not have one.

Davidson said that as a result of that findings, Northwell is encouraging people with underlying health conditions, such as hypertension and diabetes, who are potentially exposed to the virus and who might not have a fever to consult with a doctor sooner rather than later.