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Indirect transmission of Covid-19 likely in malls – Chinese scientists

A group of research scientists led by Dr. Jing Cai investigated a cluster of Covid-19 cases associated with a shopping mall in Wenzhou, China that was shut down on January 22.

The investigators wanted to determine possible modes of virus transmission among the Covid-19 confirmed patients who may have been infected while shopping.

Using RT-PCR, the gold standard for Covid-19 detection, the research team monitored and traced close contacts of the confirmed Covid-19 patients. The researchers drew on the activities and whereabouts of the patients from onset, confirmatory of disease up to their release from the hospital.

The article reported that during January 19 through February 9, Covid-19 was diagnosed for 7 mall staff from floors B1 (basement 1) – 3 and for 10 mall customers. After doing contact tracing for the diagnosed patients, COVID-19 was confirmed for 11 persons. Sixteen patients had had direct contact with other patients or had gone shopping in the mall.

No patient reported close contact with the other patients, except for those who had visited floor 7. “The possibility of customers being infected from other sources cannot be excluded. However, most customers reported early symptom onset in a concentrated time frame,” the authors wrote. “Our findings appear to indicate that low intensity transmission occurred without prolonged close contact in this mall; that is, the virus spread by indirect transmission.”

The abstract of their research states ‘Data indicated that indirect transmission of the causative virus occurred, perhaps resulting from virus contamination of common objects, virus aerosolization in a confined space, or spread from asymptomatic infected persons.’

Currently, extensive research is still lacking as to whether and how long can Covid-19 survive outside the host. The authors point out, however, that the Middle East respiratory syndrome coronavirus (MERS-CoV) can survive outside the body and stay infectious for as long as 60 minutes after aerosolization.

“Hence, the rapid spread of SARS-CoV-2 [the COVID-19 virus] in our study could have resulted from spread via fomites (e.g., elevator buttons or restroom taps) or virus aerosolization in a confined public space (e.g., restrooms or elevators),” they wrote. 

Cai J, Sun W, Huang J, Gamber M, Wu J, He G. Indirect virus transmission in cluster of COVID-19 cases, Wenzhou, China, 2020. Emerg Infect Dis. 2020 Jun [date cited].

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