recent study of nearly 140 hospitalised patients in Wuhan, China, has identified a pattern of symptoms associated with the new coronavirus, now officially known as COVID-19.

The most common symptom is fever, according to the researchers at Zhongnan Hospital of Wuhan University. They observed fevers in 99 percent of the patients in their study.

Other common symptoms include fatigue and a dry cough, which appeared in more than half of the patients studied. About a third also experienced muscle pain and difficulty breathing, though it took about five days (on average) for a patient to have difficulty breathing after first showing symptoms.

Other symptoms associated with common colds – such as a headache or sore throat – were seen in only a small number of cases.

COVID-19 symptoms

The coronavirus outbreak likely originated at a seafood market in Wuhan in December. It has since spread to 25 countries outside China, though most of the cases remain concentrated on the Chinese mainland.

So far, more than 1,100 people have died and more than 45,000 have been infected by the virus.

Learning more about the virus' symptoms could help physicians identify severe cases before a person becomes critically ill. It could also help scientists better understand how the virus spreads.

"We don't know yet the arc of how infectious someone is over the course of their infection," Lauren Meyers, an epidemiologist at the University of Texas at Austin, told Business Insider.

"We don't know if people are infectious before they have symptoms, and we are not sure how infectious they are even while they have symptoms."

Patients could spread the virus before they're hospitalised

The new study found that the virus is most likely to affect older men with preexisting health problems. More than 54 percent of the patients in the study were men, and the median age of patients was 56.

On average, it took about 10 days for patients with severe cases to be admitted to the ICU from the time their symptoms began, the researchers found. But it's possible that these patients contracted the virus long before they developed a fever.

Meyers guessed that a typical infected person is probably contagious without showing symptoms for five or more days. In total, health experts have estimated a person with COVID-19 can be contagious for between one and 14 days; one group of Chinese scientists recently suggested that people could be contagious for up to 24 days.

But according to the new study, it is taking about seven days for patients who are already showing symptoms in Wuhan to be admitted to a hospital there.

The authors didn't say why that's the case, but Reuters reported last week that hospitals in Wuhan have turned away some patients with milder symptoms.

Other infected people may choose not to admit themselves right away, since there's no cure for the virus – doctors just provide supportive care such as fluids or steroids.

Whatever the reason, that delay could help the virus spread.

"Assuming that people are not hospitalised, not isolated for the first week of their symptomatic period, then that certainly is a key opportunity for onward transmission," Meyers said.

But she added: "It's not clear necessarily how mobile those people would have even been in that week. If they're really feeling lousy and they have a fever and they're already having issues with breathing, they may not be moving around."

Early symptoms could also include diarrhoea

The new study also found that patients who ended up in the ICU had more abdominal pain and appetite loss than patients with milder coronavirus cases.

The researchers noted some early, "atypical" symptoms as well: They found that 14 patients developed diarrhoea and nausea one to two days before their fever or difficulty breathing set in.

This might suggest another way the virus is spreading. According to the study, one patient with abdominal symptoms was sent to the surgical department, since the symptoms didn't align with typical coronavirus cases.

That person went on to infect at least four other hospitalised patients – all of whom showed "atypical abdominal symptoms" as well – and at least 10 healthcare workers.

"If true, then this confirms that some patients are likely to be far more infectious than others, and this poses further difficulties in managing their cases," Michael Head, a senior global health research fellow at the University of Southampton, said in a statement.

Of the nearly 140 patients in the Zhongnan Hospital study, nearly 30 percent were healthcare workers.

Scientists still think the coronavirus is mostly transmitted through respiratory droplets such as saliva and mucus when a person coughs or sneezes.

But Meyers said diarrhoea could be a possible route of transmission, too. 

A January study from researchers in Beijing and Shanghai identified the coronavirus in stool samples from patients with diarrhoea and nausea.

Meyers pointed to one "gruesome anecdote" from the SARS outbreak in 2003, when a patient with severe diarrhoea infected hundreds of residents in his apartment complex in Hong Kong. The virus is believed to have spread through pipes, entering people's bathrooms via floor drains.

"It's too early to say how significant of a contribution diarrhoea would be to future transmission of this novel coronavirus," Meyers said.

"With SARS, diarrhoea was not a super common symptom, but it certainly occurred in a fraction of SARS patients."

Health authorities recently evacuated more than 100 people from a building in Hong Kong after two residents 10 floors apart tested positive for COVID-19. They're now investigating whether the virus can spread through sewage systems.

This article was originally published by Business Insider.

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