The case of a German adult who acquired novel coronavirus infection locally in Munich from a Chinese who hails from Shanghai is the second reported case of a person human-to-human transmission the incubation period. But a Correspondence published in the New England Journal of Medicine now sheds more light on how people who are asymptomatic for the virus can infect others.
It also reports the first known case of fourth-generation transmission (assuming that the infection was transmitted to the Chinese lady by a close contact) of the novel virus outside China.
Though nine cases of human-to-human transmission have been reported from five countries — Vietnam, Germany, Japan, the U.S. and South Korea, all local transmission had occurred only among people who had come in contact with an infected person who had recently visited China.
Even more sobering is the fact that persons recovering from illness can have huge viral load. This raises “concern about prolonged shedding of the virus even after recovery,” writes Dr. Camilla Rothe, who is the first and corresponding author from University Hospital LMU Munich, Munich, Germany.
China’s National Health Commission Minister was the first to warn that the novel virus might be spreading even during the incubation period when symptoms do not show up.
The work “suggest spread can occur from asymptomatic patients and there may be viral shedding, and risk of contagion, after recovery. If true, this will make control more challenging,” Dr. Scott Gottlieb former Commissioner of the U.S. Food and Drug Administration says in a tweet.
The Chinese lady who had arrived in Munich on January 19 was asymptomatic till January 23. She became ill on her flight back to China, where she was tested positive for novel coronavirus on January 26. Hers is a case of virus transmission during incubation period.
The German businessman met the Chinese lady of January 20-21 but developed symptoms on January 24 and recovered quickly. But he had “high viral load” of 108 copies per millilitre in his sputum sample.
Three other German employees at the same company too tested positive for the novel virus. While only one of them had contact with the Chinese lady, the other two had contracted the virus from the German businessman who first fell sick, thus extending the chain of human-to-human transmission.
Containing the spread
In the case of SARS (severe acute respiratory syndrome) people began spreading the virus only after they developed symptoms. But the novel coronavirus seems to be behaving like influenza and measles where people can spread the virus even before symptoms show up.
Unlike in the case of Ebola where the virus spread happens only after symptoms show up, symptomless spreaders like the novel coronavirus will make it difficult to contain the spread. Also, while Ebola spreads only through contact with body fluids, the novel coronavirus, SARS and influenza can spread through air droplets, making it even more easy for the virus to spread and even more difficult to contain the spread.
More studies are needed to know how infectious people with novel coronovirus are during the incubation period.
