Boris Johnson is in intensive care with COVID-19. Here's what research shows so far about outcomes in severe coronavirus cases.

awoodward@businessinsider.com (Aylin Woodward)
UK Prime Minister Boris Johnson.

Leon Neal/Pool via REUTERS/File Photo

UK Prime Minister Boris Johnson has been moved into an intensive-care unit after his condition deteriorated on Monday. Johnson was admitted to the hospital on Sunday for "persistent coronavirus symptoms" and was put in intensive care at about 7 p.m. in London on Monday, his spokesman said. 

While 80% of COVID-19 cases are considered mild — a broad term referring to patients who do not require hospitalization — severe cases can involve pneumonia-like symptoms and respiratory failure. In an intensive-care unit, some patients are placed on a ventilator that enables them to breathe. Johnson's spokesman said the 55-year-old prime minister is not on a ventilator and is in stable condition on Tuesday.

A study from the US Centers for Disease Control and Prevention found that coronavirus patients were admitted to the ICU in 4.9% to 11.5% of the 2,449 cases analyzed. About 53% of ICU admissions from February 12 to March 16 were patients older than 65.

Here's what research has found so far about the outcomes for patients admitted to the ICU.

An elderly person arriving on a stretcher to the NYU Langone Health Center hospital on March 23 in New York City.

ANGELA WEISS/AFP via Getty Images

Preliminary studies ended too soon to know longer-term outcomes for ICU patients 

Several studies have collected data about patient outcomes in the ICU, but most lasted only a few weeks — and at that point, a majority of the ICU patients in question were still in critical care. So existing research isn't sufficient to draw conclusions about what happens to ICU patients in the longer term. But in the short term, scientists have found that most ICU patients stay in the hospital at least a few weeks.

Research published Tuesday in the Journal of the American Medical Association looked at critically ill patients who were admitted to ICUs in Lombardy, Italy, between February 20 and March 18.

Of the 17, 713 people who tested positive for the coronavirus in Lombardy during that time period, 1,593 (9%) were admitted to the ICU. About 82% of those ICU patients were male. 

At the conclusion of the study on March 25, 26% of the ICU patients had died. Another 16% of patients had been discharged from the hospital, while the remaining 58% remained in intensive care.

A security worker outside St Thomas' Hospital in London after Prime Minister Boris Johnson was admitted Sunday for coronavirus symptoms.

Getty

In the UK, a study of 2,249 coronavirus patients admitted to critical care as of Friday found that 346 patients — 15% — died in the ICU. Another 15% of the critical-care patients were discharged, and the remaining 70%, 1,559 patients, were still in critical care on Saturday, when the research ended.

A smaller study in the US looked at 24 patients with COVID-19 who were admitted to the ICU in nine Seattle-area hospitals from February 24 to March 9. The findings showed that the average length of an ICU stay among surviving patients was 14 days. Half of the patients died after one to 18 days in intensive care. Four of those 12 patients had a do-not-resuscitate order.

"Mortality among these critically ill patients was high," the authors concluded.

Five of the surviving 12 patients were discharged from the hospital, four were discharged from the ICU but remained in the hospital, and three remained in the ICU on ventilators as of March 23.

A nasal ventilator pictured as a patient infected with COVID-19 was treated in a pulmonology hospital in Vannes, France, on March 20.

Reuters/Stephane Mahe

Those findings were similar to another study, published March 19, which looked at 21 patients admitted to the ICU at Washington state's Evergreen Hospital from February 20 to March 5. As of March 17, 67% of those patients had died, and 24% remained critically ill at the end of the study. Only two patients had been discharged from the ICU.

The trend held true in China, too: Of the 41 coronavirus patients first identified in Wuhan — the city where the coronavirus pandemic originated late last year — 13 were admitted to the ICU by January 4, according to a study published in the journal The Lancet. Five of those ICU patients died by January 22, while seven were discharged from the hospital. The remaining patient was still in intensive care when the research finished.

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