High SARS-CoV-2 attack rates associated with singing events

The coronavirus disease pandemic (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), continues to spread worldwide, causing over 133 million infections.

SARS-CoV-2 is spread by respiratory droplets when an infected person coughs, sneezes, speaks and breathes. In some cases, it can also be spread by singing. Previous reports have shown an outbreak of epidemics involving singing groups.

Now a team of researchers from the Netherlands and Sweden is showing that during singing it is possible to spread through the air through infectious droplets or aerosols over longer distances of more than 1.5 meters due to singing.

A study that appeared on the server before printing medRxiv *, researchers described the transmission of SARS-CoV-2 in six singing events between September and October 2020 across the Netherlands, with attack rates ranging from 25 to 74 percent.

Aerosol transfer in singing events

Previous studies and the media have described multiple epidemics with a high attack rate among singing groups between March and September 2020 in the Netherlands.

These reports suggest a potentially increased risk of singing for SARS-CoV-2 transmission. However, it was not clear whether the reported attacks were due to frequent and prolonged social contacts before, during, or after the singing event, or whether singing was a risk in itself.

As of March 2020, singing groups have stopped rehearsing in the Netherlands due to the widespread transmission of SARS-CoV-2 along with other public health measures.

When governments began lifting restrictions due to a declining number of cases, singing in groups was allowed in July 2020, provided certain recommendations were followed. This includes the following guidelines for ventilation, singing in a zigzag formation, and using a room with mandatory ventilation rates.

At the time, universal masking or wearing masks in public was still not mandatory.

In the Netherlands, about a million singers participate in 24,000 choirs, and about 70 percent of ensembles have continued their practice since September 2020. From then until October 2020, the number of weekly and COVID-19 cases in the country rose sharply, from 31.4 to 391 per 100,000.

Study

In the study, the team aimed to determine the correlation between continued singing and a rapid increase in COVID-19 cases.

From September to October 2020, they investigated six groups of COVID-19 cases among those who attended the singing events. It was reported that four groups were associated with the choir’s rehearsals, one with the choir’s performance and the other with the choir during the church service.

The team collected data by phone or email and through online questionnaires to arrive at the study’s findings. After collecting and analyzing data, the team found that the broadcast for most members of the singing group took place at singing events.

In the five events mentioned, the positive cases had little or no contact outside of the event, other than those who lived together and traveled to the event. Approximately ten people lived together, and seven of them contracted COVID-19.

Confirmed and probable cases of COVID-19 in each singing event, September - October 2020 according to the date of onset of symptoms or alternatively the date of a positive test.

Confirmed and probable cases of COVID-19 in each singing event, September – October 2020 according to the date of onset of symptoms or alternatively the date of a positive test.

Further, at least one member of the singing group reported the onset of symptoms from day 0 to 3 after the event. This shows that they are contagious during events, supporting previous studies that show a higher level of rash before symptoms develop in terms of the dynamics of SARS-CoV-2 transmission.

Indirect contact and droplet transmission within 1.5 meters due to singing is possible if excessive spread is present in the event. One of the factors that could affect the transmission is the flow of air that expels respiratory droplets over long distances.

The team recommended further studies to determine the role of airflow and transmission dynamics of SARS-CoV-2 when singing in groups. Phylogenetic analysis and serological tests should be performed to identify potential cases of the source or those that are sensitive.

The team concluded that multiple transmission routes could have caused disease outbreaks in five clusters. It is also possible that airborne transmission due to singing partly led to reported high attack rates.

Therefore, when infection control measures are allowed and gatherings are allowed, recommendations regarding singing groups are necessary to prevent the spread of the virus.

* Important notice

medRxiv publishes preliminary scientific reports that have not been reviewed and, therefore, should not be considered definitive, guide clinical practice / behavior related to health, or be treated as established information.

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