Coronavirus Study Claiming 2019-nCoV Can Spread Before Symptoms Has 'Major Flaws and Errors,' Researchers Say

A study suggesting the 2019-nCoV coronavirus could be spread before symptoms appear has "major flaws and errors," researchers have said. Questioning the findings published in the NEJM on January 30, experts say the woman was experiencing symptoms when she transmitted the virus—but she had not been interviewed by the team before they published their findings.

The outbreak, which is believed to have started in Wuhan, China, has now spread to at least 23 other countries or territories. As of February 4, the World Health Organization had confirmed 20,630 cases, as well as 426 deaths.

The NEJM article was looking at how 2019-nCoV is transmitted. It is known that the virus can be passed from person to person via the bodily fluids of someone infected. This has prompted a series of health warnings about coming into close contact with sufferers, as well as advice on limiting its spread through hygiene measures, such as washing your hands regularly.

In their letter to the NEJM, researchers said they had found evidence to suggest the virus can be transmitted by an infected person, even before symptoms had appeared—known as the incubation period. A 33-year-old German man had attended a meeting in Munich with a colleague from Shanghai. She did not appear to have any symptoms but became ill on the flight home. She later tested positive for 2019-nCoV. The otherwise healthy German man subsequently fell ill and was also diagnosed with the coronavirus.

"It is notable that the infection appears to have been transmitted during the incubation period of the index patient, in whom the illness was brief and nonspecific," the team wrote. "The fact that asymptomatic persons are potential sources of 2019-nCoV infection may warrant a reassessment of transmission dynamics of the current outbreak."

Their findings were reported on globally, with some suggesting this would explain why the virus is spreading so fast. It could also make containing it far more difficult.

However, in an article in Science Magazine, experts have now called the research into question. Researchers with the Robert Koch Institute (RKI), Germany, have written to the NEJM to say they believe the evidence presented was flawed.

One of the letter's authors, Michael Hoelscher, from the Ludwig Maximilian University of Munich Medical Center, said that after talking to the Shanghai patient, it emerged she had been displaying symptoms during her meeting with the German man. She had been suffering from muscle pain and fatigue, and had taken paracetamol.

It appears the woman had not been contacted to ask if she was symptomatic, with the researchers instead relying on anecdotal reports of her health from other people. The RKI has reportedly told the WHO about its concerns over the NEJM paper.

In an article about the potential for coronavirus to spread before symptoms, Sweden's Public Health Agency said the suggestion "lacked scientific support," adding that the NEJM article was "subsequently proven to contain major flaws and errors."

The news comes as scientists prepare to give 2019-nCoV an official name. Researchers are concerned that unofficial names for the virus are spreading online and could cause stigma. "The danger when you don't have an official name is that people start using terms like China Virus, and that can create a backlash against certain populations." Crystal Watson, from the Johns Hopkins Center for Health Security," told the BBC.

The WHO is yet to declare the outbreak a "pandemic," which it defines as a "worldwide spread of a new disease." At a press conference, Sylvie Briand, director of the WHO's Infectious Hazards Management Department, said this status has not been declared because they believe the measures currently in place can curb the spread of 2019-nCoV.