Widespread SARS-CoV-2 Transmission Among Attendees at a Large Motorcycle Rally and their Contacts, 30 US Jurisdictions, August–September, 2020

Abstract The 2020 Sturgis Motorcycle rally resulted in widespread transmission of SARS-CoV-2 across the United States. At least 649 COVID-19 cases were identified, including secondary and tertiary spread to close contacts. To limit transmission, persons attending events should wear masks and practice physical distancing. Persons with a known exposure should quarantine and obtain COVID-19 testing.


Introduction
Large gatherings such as weddings, sporting competitions and church events can result in significant SARS-CoV-2 transmission [1][2][3][4]. A major event, the Sturgis Motorcycle Rally (Sturgis Rally), was held in Meade County, South Dakota, August 7-16, 2020, with approximately 462,000 persons* attending a variety of outdoor and indoor activities.
Local news media reported COVID-19 cases identified in Sturgis during the rally and among attendees shortly after the event. Here we present a national count of reported COVID-19 cases indicating geographic spread from those returning from the rally.

Methods
To summarize the number of COVID-19 cases associated with attendance at the Sturgis Rally and describe the geographic spread of cases across the United States (US), the Centers for Disease Control and Prevention (CDC) requested information on laboratory or clinically diagnosed COVID-19 cases † detected after travel to Sturgis/Meade County, South Dakota (SD), August 1-30, or attendance at the Sturgis Rally, August 7-16, from 54 health departments (50 states and Washington, DC, New York City, Chicago and Los Angeles County). Information on risk factors and travel in the previous two weeks was collected by health department staff via phone interviews with infected persons. Several states modified the definition of a Sturgis Rally-associated case to include cases who reported any travel to SD during August due to some individuals' reluctance to disclose attendance at the Sturgis Rally. Data requested included total numbers of confirmed and probable cases of COVID-19 in index (primary) patients and close contacts^ (secondary/tertiary), and demographic characteristics and clinical outcomes for primary cases. Secondary cases were defined as laboratory or clinically diagnosed infections A c c e p t e d M a n u s c r i p t among persons who were close contacts of a person who attended the Sturgis Rally or traveled to SD, August 1-30. Tertiary cases were infections in close contacts of persons with secondary infections. Epidemiologic data were summarized across participating jurisdictions.
This activity was reviewed by CDC and was conducted consistent with applicable federal law and CDC policy. †

Results
Of 54 jurisdictions, 39 (72%) provided data. Nine jurisdictions reported no cases, 30 reported one or more Sturgis-associated # COVID-19 cases ( Figure 1). Of 649 reported cases, 463 (71%)laboratory-confirmed or probable primary cases were reported by 30 jurisdictions from across the country with most laboratory-confirmed cases diagnosed within two weeks of the Sturgis Rally. An additional 186 (29%) secondary and tertiary cases were reported by 17 jurisdictions. Among the 463 primary cases, 17 (3.7%) persons were hospitalized and one died (Table 1). South Dakota and five bordering states (Minnesota, Montana, North Dakota, Nebraska, Wyoming) reported 56% of all cases.

Public Health Response
In South Dakota, several public health mitigation activities were implemented before, during, and after the event. During the event, the SD Department of Health (DOH) issued four public health alerts (https://doh.sd.gov/news/recent-releases.aspx) to inform the A c c e p t e d M a n u s c r i p t public about new COVID-19 cases identified in local bars and a tattoo parlor in Sturgis and to advise on testing. Testing capacity in Meade and surrounding counties was increased in anticipation of the event through the placement of additional diagnositic equipment to conduct testing using SARS-CoV-2 real-time reverse transcription polymerase chain reaction assay (RT-PCR) to identify cases before they returned to other regions of the state. In Sturgis, the SD DOH also coordinated with a large health system to support testing for city residents. From August 1 to September 15, the 14-day testing volume among Meade County residents increased 199% and the 14-day PCR test positivity increased, from 5% to 8%, indicating the event's impact on SARS-CoV-2 transmission in Meade County for both workers and county residents. Through media briefings and health department websites, the bordering states of North Dakota and Minnesota encouraged residents who attended or worked at the event to obtain COVID-19 testing.

Discussion
Attendance at the Sturgis Rally led to widespread SARS-CoV-2 transmission to 463 people in 30 jurisdictions, with 17 jurisdictions reporting subsequent transmission to 186 household and workplace contacts. In Minnesota, epidemiologic investigations identified secondary and tertiary transmission from attendees who traveled to Sturgis and traced Rally-associated cases across one-third of its counties [5].

Conclusion
These findings highlight the risk of COVID-19 transmission associated with a mass gathering event that resulted in preventable illness, hospitalizations, and at least one reported death across multiple jurisdictions. The Sturgis Rally had many characteristics of a superspreading event: large crowds, high intensity of contact between people, potential for highly infectious individuals traveling from hotspots, and events in poorly ventilated indoor environments. Although specimens were not available for whole genome sequencing to identify this as a super-spreading event, the event resulted in secondary transmission of COVID-19 to those who did not attend the event, particularly within South Dakota and bordering states. Such mass events can result in the resurgence of COVID-19 in counties and states even after epidemic control has been achieved through local risk mitigation activities. Recent modeling suggests that interventions such as postponing voluntary, mass events may be the most viable option to maintain epidemic control [10].
If postponement is not an option, public messaging should signal the risks and inform those who choose to attend gatherings about COVID-19 mitigation strategies to protect themselves during and after the event, including symptom monitoring and quarantine** and to protect their household members and community when they return home. To limit transmission, persons attending events should wear masks and practice physical distancing. In the absence of state or local restrictions on gatherings, health departments may consider direct outreach to businesses and business associations whose workers and A c c e p t e d M a n u s c r i p t patrons will be at risk during the event to implement mitigation strategies (e.g., operating at reduced capacity, risk communication tailored to the event). Additional strategies include offering mass COVID-19 testing to attendees during and after the event to identify cases as soon as possible, ideally before travel back home if residing in another state.
A c c e p t e d M a n u s c r i p t Notes M a n u s c r i p t   Did not provide data