Old age, sepsis and “blood clotting issues” may increase a coronavirus patient’s risk of death, research suggests.
Since the coronavirus strain Covid-19 emerged at a seafood and live animal market in the Chinese city Wuhan at the end of last year, experts have been rushing to identify the most vulnerable patients.
Data suggests four out of five cases are mild, with a minority succumbing to pneumonia.
To learn more, scientists in China looked at 191 confirmed cases treated across two Wuhan hospitals, of whom 54 died.
“Older age, showing signs of sepsis on admission, underlying diseases like high blood pressure and diabetes, and the prolonged use of non-invasive ventilation were important factors in the deaths of these patients,” said study author Dr Zhibo Liu.
“Poorer outcomes in older people may be due, in part, to the age-related weakening of the immune system and increased inflammation that could promote viral replication and more prolonged responses to inflammation, causing lasting damage to the heart, brain, and other organs.”
One expert added “increased age” is a common risk factor for “nearly all infections”.
Since Covid-19 was identified at the end of last year, the strain has been confirmed in more than 100 countries across every inhabited continent.
Twenty-one countries have just one confirmed patient.
Since the start of the outbreak, more than 114,000 patients have tested positive for the virus, of which over 64,000 have “recovered”, according to John Hopkins University data.
Globally, the death toll has exceeded 4,000.
Cases appear to have “peaked” in China, the epicentre of the outbreak.
The infection has taken hold elsewhere, however, with Italy identifying more than 9,000 patients and 463 deaths.
The UK has 319 confirmed cases, with five Britons succumbing to pneumonia.
What are the risk factors linked to dying from the coronavirus Covid-19?
The Chinese scientists looked at patients admitted to Jinyintan or Wuhan Pulmonary hospitals after 29 December 2019.
These were the designated hospitals patients with severe coronavirus were transferred to from across the city until 2 February.
The participants had been discharged, or died, by 31 January.
Medical records, treatment data and laboratory results were compared between the survivors of the infection and the deceased.
Using mathematical models, the scientists examined risk factors associated with dying of the infection.
Overall, just under half (48%) of the patients had an underlying condition.
Blood pressure was the most common, making up 30% of the co-morbidities, followed by diabetes at 19%.
From illness onset, most spent 22 days in hospital before being discharged. The average time to death was 18.5 days.
The survivors were on average 52 years old, compared to 69 among the deceased.
As well as old age, death was linked to a higher score on the Sequential Organ Failure Assessment – a measure of sepsis – upon hospital arrival.
Those who eventually died also had elevated levels of the protein d-dimer, a marker of blood clots.
The immune-fighting protein interleukin 6 – a sign of inflammation – was also raised, while the white blood cells lymphocytes were markedly lower.
Overall, all the deceased (100%) had sepsis, versus less than half (42%) of the survivors.
Sepsis occurs when the body over-reacts to an infection, releasing excessive amounts of pathogen-fighting chemicals that can damage multiple organ systems.
Nearly all (98%) of the fatalities developed respiratory failure compared to 36% of the survivors.
This occurs when insufficient levels of oxygen pass from the lungs to the blood or the lungs cannot remove carbon dioxide efficiently enough.
Secondary infections, which come about when an already ill person is more vulnerable to an additional pathogen, affected half (50%) of the deceased.
Just 1% of the survivors were diagnosed with an infection that was not the coronavirus.
“The risk factors for death of severe illness and increased age are already recognised, and common to nearly all infections,” said Professor Keith Neal from the University of Nottingham.
“Underlying health conditions associated with infection has also been previously reported.”
The scientists also found the survivors “shed” the virus for an average of 20 days, while the deceased remained infectious until the time of death.
They noted, however, viral shedding is influenced by disease severity.
“The extended viral shedding noted in our study has important implications for guiding decisions around isolation precautions and anti-viral treatment in patients with confirmed Covid-19 infection,” said co-lead author Professor Bin Cao.
“However, we need to be clear that viral shedding time should not be confused with other self-isolation guidance for people who may have been exposed to Covid-19 but do not have symptoms, as this guidance is based on the incubation time of the virus.”
The incubation period is the time between infection and the onset of symptoms.
Although the scientists mentioned anti-viral treatment, there is no “set” therapy for Covid-19.
Most patients fight off the infection naturally, with some requiring “supportive care” – like ventilation – while their immune system gets to work.
When it comes to symptoms, the scientists noted the survivors and deceased both endured fever for around 12 days.
Cough, another tell-tale symptom, appeared to be more persistent.
Just under half (45%) of the patients still had a cough when discharged.
Shortness of breath lasted until day 13 among the survivors, but continued until death for the deceased.
“The key finding this paper adds is the prolonged virus shedding and the recovered patients main remain infectious for longer than previously thought,” said Professor Neal.
“This has implications for isolating recovered patients, which can easily be implemented in most instances.”
The scientists noted their study had several limitations.
Hospitalised patients are severe by definition. Excluding mild cases skews the risk factors linked to coronavirus mortality.
Viral shedding was also estimated according to swabs and other “specimen collections”, which were not gathered throughout the study period, the scientists wrote in The Lancet.
Covid-19’s death rate has been up for debate.
The World Health Organization claimed it had killed 3.4% of patients globally on 3 March, higher than its past estimate of 2%.
Experts called this a likely “overestimate”, adding a 1% mortality rate seems more “reasonable”.
What is the new coronavirus Covid-19?
Covid-19 is one of seven strains of the coronavirus class that are known to infect humans.
The class is also made up of four strains that cause the common cold, severe acute respiratory syndrome (Sars) and Middle East respiratory syndrome (Mers).
Sars killed 774 people during its 2002/3 outbreak, while 858 people died in Mers’ 2012 outbreak.
Most of those who initially caught Covid-19 worked at, or visited, the “wet market” in Wuhan.
Officials confirmed early on in the outbreak the virus spreads face-to-face via droplets that have been sneezed or coughed out by a patient.
There is also evidence it may be transmitted in faeces and urine.
In severe cases, pneumonia can come about when the infection causes the alveoli (air sacs) in the lungs to become inflamed and filled with fluid or pus.
The lungs then struggle to draw in air, resulting in reduced oxygen in the bloodstream.