key: cord-336963-evjmz49u
authors: Chen, Dong; Hu, Chenchan; Su, Feifei; Song, Qifa; Wang, Zhen
title: Exposure to SARS-CoV-2 in a high transmission setting increases the risk of severe COVID-19 compared to exposure to a low transmission setting?
date: 2020-06-05
journal: J Travel Med
DOI: 10.1093/jtm/taaa094
sha: 
doc_id: 336963
cord_uid: evjmz49u

nan

reported in other provinces of China (WHO situation report, 27 February 2020). The striking difference in mortality between Wuhan and other cities in China was partly attributed to insufficient medical services at the time when the health care system was overwhelmed in Wuhan. 1 However, the higher mortality persisted in Wuhan despite the fact that after the initial epidemic peak same clinical management guidelines were applied throughout China, and case fatality rates remained higher even when more medical personnel was deployed to Wuhan. Similarly, in the epicentre in Northern Italy, a very high case fatality rate was reported during the height of the outbreak. 6 The high mortality in Northern Italy was also initially attributed to the fact that hospitals were overwhelmed by the onstorm of cases.

But maybe there is another factor inherent to high transmission settings that lead to a higher case fatality rate as observed in our study? In our study, we were able to exclude any differences in healthcare systems and clinical management as a confounding factor for severity.

In conclusion, our study highlights that SARS-CoV-2 infection in a hotspot or epicentre with high transmission intensity may adversely impact mortality rates compared to infection in a low transmission area. We hypothesize that repeat or constant exposure to the widely circulating virus could explain this phenomenon.

However, our study was only an observational study, and can only provide indirect ecological evidence. More studies in other settings and countries are necessary to elucidate to what extent repeat exposure may increase the risk of more severe COVID-19 disease outcomes and relevant immunological mechanisms.

U N C O R R E C T E D M A N U S C R I P T

University and Sixth People's Hospital of Wenzhou. Oral consent was acquired from all patients.

*These authors contributed equally to the article. All authors read and approved the final manuscript.

All authors declare no conflict of interests. Table 1 . Comparison and multivariate analysis of epidemiological and clinical features between the group exposed to a high-epidemic area and the group exposed to a low-endemic area 

Potential association between COVID-19 mortality and health-care resource availability

Correlation between travellers departing from Wuhan before the Spring Festival and subsequent spread of COVID-19 to all provinces in China

Clinical features of patients infected with 2019 novel coronavirus in Wuhan, China

This study was supported by Key scientific and technological innovation projects of Wenzhou (ZY202004) and Natural Science Foundation of Ningbo (2017A610273).