Coronavirus outbreak: People can spread the infection even before symptoms set in, shows evidence
Even people who show no symptoms of the new coronavirus can spread the disease, which has claimed 361 lives and infected over 17,200 in China.
This development comes, according to a new report, which shows that a 33-year-old German businessman got the disease from a Chinese colleague — who did not show any signs or symptoms of infection in Germany — but fell ill on her flight back to China.
"This case of 2019-nCoV infection was diagnosed in Germany and transmitted outside of Asia. However, it is notable that the infection appears to have been transmitted during the incubation period of the index patient (Chinese business partner), in whom the illness was brief and nonspecific," say researchers in their findings.
The report is the first scientific evidence made available to the public that the Wuhan coronavirus can be spread before someone shows any symptoms, state the findings published in The New England Journal of Medicine.
An earlier Lancet study stated that people infected with Wuhan Coronavirus may not even know they are carrying the disease since there might be no visible symptoms.
The case study showed that six members of a family from Shenzhen, China, were infected, but one child with the virus did not show any symptoms. The 10-year-old child was later confirmed virologically to have an asymptomatic infection.
According to the current case study, the "otherwise healthy" German businessman (described as patient 1) became ill with a sore throat, chills, and myalgias on January 24, 2020.
"The following day, a fever of 39.1°C (102.4°F) developed, along with a productive cough. By the evening of the next day, he started feeling better and went back to work on January 27," says the team.
The team comprised members from University Hospital LMU Munich, Munich, Germany, Klinikum München-Schwabing, Munich, Charité Universitätsmedizin Berlin, Berlin, and Bundeswehr Institute of Microbiology, Munich.
The researchers say, before the onset of symptoms, he had attended meetings with a Chinese business partner at his company near Munich on January 20 and 21. The business partner, a Shanghai resident, had visited Germany between January 19 and 22.
"During her stay, she had been well with no signs or symptoms of infection but had become ill on her flight back to China, where she tested positive for 2019-nCoV on January 26 (index patient)," says the study.
On January 27, she informed the company about her illness. Subsequently, the German colleague was sent to the Division of Infectious Diseases and Tropical Medicine in Munich for further assessment.
When he came to the Munich clinic, he did not have a fever and appeared well. He reported no previous or chronic illnesses and had no history of foreign travel within 14 days before the onset of symptoms.
However, two nasopharyngeal swabs and one sputum sample were obtained and were found to be positive for 2019-nCoV, say experts.
On January 28, three additional employees at the company tested positive for 2019-nCoV — described as patients 2 to 4 in the paper. Of these patients, only patient 2 had contact with the Chinese business partner. The other two patients only had contact with the German colleague.
All the patients with confirmed 2019-nCoV infection were admitted to a Munich infectious diseases unit for clinical monitoring and isolation. So far, none of the four confirmed patients show signs of severe clinical illness.
"The fact that asymptomatic persons are potential sources of 2019-nCoV infection may warrant a reassessment of transmission dynamics of the current outbreak," says the team.
They say: "In this context, the detection of 2019-nCoV and a high sputum viral load in a convalescent patient (patient 1) arouse concern about prolonged shedding of 2019-nCoV after recovery."
The US Centers for Disease Control and Prevention (CDC) says that typically, with most respiratory viruses, people are thought to be most contagious when they are most symptomatic (the sickest).
However, with 2019-nCoV, there have been reports of spread from an infected patient with no symptoms to close contact, says the CDC, referring to the German study.
The World Health Organization (WHO) last week declared the Wuhan coronavirus outbreak as a global health emergency. Since then, the first death outside China from the new coronavirus was recorded on Sunday in the Philippines.
The WHO's situation report on the 2019-nCoV recommends limiting human-to-human transmission, including reducing secondary infections among close contacts and healthcare workers, preventing transmission amplification events and preventing further international spread from China.
According to WHO experts, during previous outbreaks due to other coronaviruses — Middle-East Respiratory Syndrome (MERS) and Severe Acute Respiratory Syndrome (SARS) — human-to-human transmission occurred through droplets, contact, and fomites, suggesting that the transmission mode of the 2019-nCoV can be similar.
"WHO is providing guidance on early investigations, which are critical to carrying out early in an outbreak of a new virus," says the organization.
"The data collected can be used to refine recommendations for surveillance and case definitions, to characterize the key epidemiological transmission features of 2019-nCoV, help understand spread, severity, impact on the community and to inform operational models for implementation of counter-measures such as case isolation, contact tracing, and isolation," adds WHO.