High Contagiousness and Rapid Spread of Severe Acute Respiratory Syndrome Coronavirus 2

Abstract

S evere acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the etiologic agent of the current rapidly growing outbreak of coronavirus disease (COVID-19), originating from the city of Wuhan, Hubei Province, China (1). Initially, 41 cases of "pneumonia of unknown etiology" were reported to the World Health Organization by the Wuhan Municipal Health Committee at the end of December 2019 (2). On January 8, 2020, the pathogen was identified (1), and human-to-human transmission was reported soon after. By January 21, most provinces of China had reported COVID-19 cases. By March 16, the outbreak had led to >170,000 total confirmed cases and >6,500 deaths globally. In a period of 3 months, an outbreak of apparent idiopathic pneumonia had become the COVID-19 pandemic.Studying dynamics of a newly emerged and rapidly growing infectious disease outbreak, such as COVID-19, is important but challenging because

Fast spread of COVID-19 in Europe and the US suggests the necessity of early, strong and comprehensive interventions

“…https://doi.org/10.1101/2020.04.04.20050427 doi: medRxiv preprint estimated to be between 2-3 (2-5) and were widely reported in official documents (17) and public media. These estimates are mostly based on an epidemic growth rate between 0.1 and 0.14/day (2)(3)(4)(5), which is inconsistent with many new lines of evidence and data as discussed in this paper and a previous work (6). Previously we showed that with a mean serial interval, defined as the duration of time between onset of symptoms in an index case and a secondary case, of 6-9 days (3,18) and an epidemic growth rate between 0.19-0.29/day, the value of R0 must be higher than 3 (6).…”

“…Using the same framework as in Ref. 6, we find that when the growth rate is 0.19/day, the median R0 is estimated to be 4.0 (95% CI: 3.1 and 5.0); whereas when the growth rate is 0.29/day, the median R0 is estimated to be 7.1 (95% CI: 5.1 and 9.6). Although shorter serial intervals are reported in the literature (19,20), it was noted that this is likely due to strong intervention efforts (18,19).…”

“…is a semi-linear function of . Note that the time from infection to case confirmation, 1/ , can be a time dependent function as we and others shown previously (6,13). To keep the model simple, we implicitly assume that the time dependent changes in can be included in the estimation of ( ).…”

“…Second, it sets the baseline for evaluation of effectiveness of intervention strategies. Third, it is important for accurate estimation of the basic reproductive number, R0, which in turn is used for many control measures, including evaluation of the vaccine/herd immunity threshold needed to stop transmission (6,8). However, a major challenge to the inference of the growth of COVID-19 is that as a result of a fast-growing outbreak and a sizable infected population with no or mildto-moderate symptoms (9,10), case confirmation data is influenced by many factors in addition to the true epidemic growth, including substantial underreporting (11), i.e.…”

The Potential role of Particulate Matter in the Spreading of COVID-19 in Northern Italy: First Evidence-based Research Hypotheses

“…rate in Italy was 0,19 per day with a doubling time close to 3.6 days in according withSanche et al (2020) who showed a growth rate of infection of COVID-19 in Wuhan, Hubei Province (China) on January 2020 close to 0.21-0.30 per day with a doubling time of 2.3-3.3[27]. The basic reproductive number (R 0 ), estimated by the researchers, was 5.7 consistently with a "super-spread event"by an airborne droplet transmission as described by Wellings and Teunis (2004) for the epidemic curves for Sever Acute Respiratory Sindrome (SARS) during the outbreak on February-June 2003 in Hong…”