Indirect Virus Transmission in Cluster of COVID-19 Cases, Wenzhou, China, 2020
When faced with an emerging infectious disease that has created a pandemic, studying every aspect of the disease is crucial to better understand transmission and to do a proper risk assessment. There is literature that shows the transmission of SARS-CoV-2 is primarily spread through droplets and close contact, however, this does not explain all cases. A recently published study in the journal Emerging Infectious Diseases investigated possible modes of transmission in a cluster of COVID-19 cases.1
A cluster of COVID-19 patients associated with a shopping mall was reviewed. Only one of the 17 cases associated with the mall had a travel history to Wuhan. This patient traveled to Wuhan 28 days prior to the onset of symptoms. This is an extremely long incubation period. There is no way to know for sure if this is patient zero in the mall cases. However, it is possible that this patient was an asymptomatic carrier with a persistent infection leading to the infection of the other cases.
Close contact at the mall was traced back to 11 cases, sixteen had direct contact with another patient or admitted to going shopping at the mall. Seven of the patients worked in the same room. Though the remaining patients denied any contact with the seven employees, they did use common facilities such as restrooms and elevators.
The rapid spread observed in these cases indicates possible spread through fomites or virus aerosolization in confined spaces. This is of value to the dental community as we often work in confined spaces producing many aerosols. More research will surely emerge as we continue to learn about the transmission routes of this novel virus. Better control of aerosols in dental settings are going to be crucial going forward.
The authors acknowledge that they cannot exclude the possibility of an unknown infected person, however to the best of their knowledge the asymptomatic carrier appears to be the start of the cluster of infections. In conclusion, the authors state “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.”
Aerosols have been a concern in recent years, how will you try to reduce aerosols when practicing in the future? By all indication screening patient’s temperature is not enough to protect ourselves and other patients, does taking patient’s temperature make you feel safer, or are you still concerned considering the increasing evidence of asymptomatic carriers? Does this study help you better understand how easily this virus can be spread in confined spaces, like operatories? Should we limit the number of people that can come back into the operatory when treating patients to prevent the possible spread?
- 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