Cases, Clusters and Outbreaks - definitions

In the Superspreading Events database, we try to establish how many people were infected at the event itself, because this helps us to guage the risks involved in that situation.  However, press reports often refer to the total number of cases linked to a superspreading event.  Linked cases include those in the wider community arising from the superspreading event.  For example, if 20 people were infected at a party, and some of those people infected 30 household members, an epidemiological investigation would conclude that 50 cases were linked to the party.  But in terms of assessing the risks of a setting, there are important differences.  Index and Secondary CasesAn index case at an event is a person who brings the infection there.  There may be more than one.  Index cases are also known as 'Primary cases'.Secondary cases are people who became infected in this setting.Tertiary cases are people who later became infected by secondary cases, eg when they went home or to other…

Superspreading Database Now Has 1500+ Entries

From all continents, including Antarctica.

Superspreading Event at Choir Practice in Catalonia

Looks like just about every risk factor was present in the setting:a lot of peopleclose togetherindoorspoor ventilationlong durationsingingGoogle Translate: The Public Health Agency assumes that the contagion took place during the general rehearsal that the choir did on Friday, September 11 in a place of La F├ábrica while preparing the concert that took place the following Sunday during the Festa Major of Sallent.

An exposure of more than 15 minutes, in a room with closed windows, with insufficient physical distance, with working air conditioning, which favors the suspension of particles by aerosol in a closed cycle, and the fact that many of the singers do not they wore masks, it potentiated the almost general contagion in an environment where it was sung, they have claimed.

Choir members have explained that they closed the windows because there was a plague of boxwood butterflies outside, and that once closed, they turned on the air conditioning. Video of the event: 
This is…

Where Are All the Movie-Theater COVID-19 Cases?

Neal Pollack asks an interesting question: I’ve been looking, very hard, for any reported evidence, because I don’t want even vaguely encourage people to make a deadly choice. But there hasn’t been one reported COVID-related death to movie theater attendance anywhere in the world. There hasn’t even been a reported case of COVID. Not a symptomatic case. Not an asymptomatic case. Nothing.
How can that be possible? Movie theaters aren’t open in Los Angeles or New York right now, but they are open most other places. Seventy percent of all screens in the United States are operating, not at full capacity, but available for customers. The coronavirus hasn’t gone away. So where are the cases? Not one case in six months. Nine months, really, when you consider that the plague started in China in December. Again, how can that be possible?
Read more.  There are no movie theater superspreading events in the database.  Yet: the Centers for Disease Control and Prevention (CDC) includes going to a movie …

First Suspected Superspreading Event on a Flight

To assess the role of in-flight transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), we investigated a cluster of cases among passengers on a 10-hour commercial flight. Affected persons were passengers, crew, and their close contacts. We traced 217 passengers and crew to their final destinations and interviewed, tested, and quarantined them. Among the 16 persons in whom SARS-CoV-2 infection was detected, 12 (75%) were passengers seated in business class along with the only symptomatic person (attack rate 62%). Seating proximity was strongly associated with increased infection risk (risk ratio 7.3, 95% CI 1.2–46.2). We found no strong evidence supporting alternative transmission scenarios. In-flight transmission that probably originated from 1 symptomatic passenger caused a large cluster of cases during a long flight. Guidelines for preventing SARS-CoV-2 infection among air passengers should consider individual passengers’ risk for infection, the numbe…

Which US States Make Contact Tracing Data Public?

NPR with a useful overview and more information per state:

The Role of AC Systems in Nursing Home Superspreading Events

Nursing homes are the most common setting for superspreading events in the database. How can the virus spread so easily in them?

A confidential report of the Dutch scientific advisory board RIVM may provide an answer. It states that the HVAC system in a nursing home in the Netherlands likely caused an outbreak that infected up to 21 residents and 18 staff members.

Below is a (slightly manually improved) Google Translate of an article in Dutch newspaper De Volkskrant.
The main findings that are suggestive of aerosol transmission via the HVAC system:
- All staff members in the nursing home wore surgical masks (except during breaks) - Only one patient was initially infected but the virus then spread rapidly throughout the facility
- The virus was found in high values ​​on the mesh covers of the air-conditioning unit and in filters of four ventilation cabinets.