CORONAVIRUS

An analysis of three Covid-19 outbreaks: how they happened and how they can be avoided

An office, a restaurant and a bus were the settings for multiple infections that have been studied in detail by health authorities. Their conclusions offer valuable lessons for the deescalation process

A crowded restaurant to celebrate the Chinese New Year; 100 workers infected inside a 19-story building; a group of devout Buddhists travelling by bus for a religious ceremony. These were the scenarios for three outbreaks of Covid-19 that have been carefully documented by the authorities. What happened in each one? What were the risk factors? What lessons can be learned, now that we are trying to get back to normal and return to restaurants, offices and other shared spaces?

The office

In a single wing of a call center in Seoul, in South Korea, the risk of infection was multiplied by four key factors: close, prolonged contact between numerous people, in an enclosed space.


Research carried out by local authorities revealed that almost all the people infected in a 19-story building with more than a thousand residents and office workers were confined to this area. Moreover, those infected were almost exclusively working in the same room. Despite the considerable interaction between workers from different floors of the building in the elevators and the lobby, the spread of the virus was largely confined to that one space filled with employees sitting at desks, “indicating that the duration of the interaction (or contact) was probably the main facilitator for extensive infection,” according to the Seoul authorities’ report.

Recommendations from scientists and health experts aim to diminish the risk by avoiding large concentrations of people with measures ranging from taking turns to remote work to using physical protection such as masks and preventing employees from sharing office materials. The recommendations also include physically distancing staff by cutting out big meetings and keeping numbers low at access points and in food and drink zones; spaces should also be properly ventilated. “We must reduce the concentration of people and exposure time, the time they spend together,” says Maricruz Minguillón, a researcher at the Spanish National Research Council’s Institute of Environmental Assessment and Water Studies (IDAEA-CSIC). “If we reduce both factors, we reduce the risk.”

How it can be avoided

Natural ventilation to avoid the recirculation of infected particles

Avoid concentrations of employees either in meetings or in food and drink zones

2 m.

Organize workstations in a zig-zag pattern and maintain a distance of two meters between each

Avoid physical contact.

No sharing of material or equipment between co-workers without prior disinfection

Keep staff distanced by combining teleworking with flexitime

How it can be avoided

Avoid concentrations of employees either in meetings or in food and drink zones

Natural ventilation to avoid the recirculation of infected particles

2 m

Organize workstations in a zig-zag pattern and maintain a distance of two meters between each

Avoid physical contact.

No sharing of material or equipment between co-workers without prior disinfection

Keep staff distanced by combining teleworking with flexitime

How it can be avoided

Natural ventilation to avoid the recirculation of infected particles

Avoid concentrations of employees either in meetings or in food and drink zones

2 m

Organize workstations in a zig-zag pattern and maintain a distance of two meters between each

Avoid physical contact.

No sharing of material or equipment between co-workers without prior disinfection

Keep staff distanced by combining teleworking with flexitime

How it can be avoided

Natural ventilation to avoid the recirculation of infected particles

Avoid concentrations of employees either in meetings or in food and drink zones

Keep staff distanced by combining teleworking with flexitime

2 m

Organize workstations in a zig-zag pattern and maintain a distance of two meters between each

Avoid physical contact.

No sharing of material or equipment between co-workers without prior disinfection

The restaurant

A New Year’s meal in the Chinese city of Guangzhou on January 24 provides the best example of how to reduce indoor risks. This scenario has been analyzed in detail in two different studies (1, 2) by the Chinese health authorities, who concluded that poor ventilation can be a decisive risk factor if contact is maintained during prolonged periods. Again, time plus social proximity multiplies the risks.


Cameras on the premises show that those infected had no contact in the washrooms or elsewhere that could have led to the transmission of the virus. Although close contact can play an important role in the transmission of SARS-CoV-2, transmission of the virus in small airborne droplets “in crowded, poorly ventilated rooms” is also possible, according to the scientists. Outdoor air vents in the restaurant were closed. “Our study suggests that it is vital to prevent overcrowding and provide good ventilation in buildings and public transportation to prevent the spread of SARS-CoV-2,” they add. The recommendations from the health authorities invariably insist on avoiding recirculating air, as well as holding activities outside whenever possible.

How it can be avoided

Avoid background music so people don’t have to raise their voices and expel more droplets as they speak

Open windows even if it makes people feel uncomfortably warm or cold

Avoid the recirculation of air

2 or 3 m

Reduce

the size of

indoor

gatherings

Whenever possible, hold

the event outdoors

Increase

the distance

between people

How it can be avoided

Avoid background music so people don’t have to raise their voices and expel more droplets as they speak

Open windows even if it makes people feel uncomfortably warm or cold

Avoid the recirculation of air

2 or 3 m

Reduce

the size of

indoor

gatherings

Whenever possible, hold

the event outdoors

Increase

the distance

between people

How it can be avoided

Open windows even if it makes people feel uncomfortably warm or cold

Avoid background music so people don’t have to raise their voices and expel more droplets as they speak

Avoid the recirculation of air

Always use air filters

Reduce the size

of indoor gatherings

2 or 3 m

Increase the distance between people

Whenever possible, hold

the event outdoors

How it can be avoided

Open windows even if it makes people feel uncomfortably warm or cold

Avoid background music so people don’t have to raise their voices and expel more droplets as they speak

Avoid the recirculation of air

Always use air filters

Reduce the size

of indoor gatherings

2 or 3 m

Increase the distance

between people

Whenever possible, hold

the event outdoors

The bus

Chinese authorities and researchers from US universities are analyzing an outbreak at a Buddhist ceremony that was attended by people travelling on two buses for a total of 100 minutes – 50 minutes each way. A woman with symptoms was traveling on one of the vehicles, where the air was recirculated; 23 passengers were infected. “Patient 0 in this outbreak appears to have been a superspreader,” explains Emily Gurley, an epidemiologist at Johns Hopkins University. “As at the restaurant, transmission could be explained by aerosols and droplets traveling longer distances due to the draft from the window or the air conditioning,” she adds.


A number of studies in Japan and elsewhere show that public transportation is not responsible for multiple infections as long as users maintain the rules of hygiene and protection, especially the use of masks that prevent infected individuals from releasing contagious droplets into the atmosphere, as happened with patient 0 on the coach. It is also suggested that specific protection measures be introduced for drivers of public transportation, as well as improving ventilation and increasing the regularity of coaches and trains in order to reduce crowding.

How it can be avoided

In any setting in which people are together for a prolonged period, these measures should be taken, prioritizing those that are most effective at protecting us from the risk of infection.

+

Physical distance

•Teleworking

• Reducing number

of employees in offices

Effectiveness

Engineering control

• Creating physical barriers

between people

Administrative

control

Protection

• Redistributing

responsibilities

to reduce contact

between people

• Mandatory use

of non-medical

masks

How it can be avoided

In any setting in which people are together for a prolonged period, these measures should be taken, prioritizing those that are most effective at protecting us from the risk of infection.

+

Physical distance

•Teleworking

• Reducing number

of employees in offices

Effectiveness

Engineering control

• Creating physical barriers

between people

Administrative

control

Protection

• Redistributing

responsibilities

to reduce contact

between people

• Mandatory use

of non-medical

masks

How it can be avoided

In any setting in which people are together for a prolonged period, these measures should be taken, prioritizing those that are most effective at protecting us from the risk of infection.

•Teleworking

• Reducing number

of employees in offices

+

Physical distance

Effectiveness

• Creating physical barriers

between people

Engineering control

• Redistributing responsibilities

to reduce contact between people

Administrative

control

• Mandatory use

of non-medical masks

Protection

How it can be avoided

In any setting in which people are together for a prolonged period, these measures should be taken, prioritizing those that are most effective at protecting us from the risk of infection.

•Teleworking

• Reducing number

of employees in offices

+

Physical distance

Effectiveness

• Creating physical barriers

between people

Engineering control

• Redistributing responsibilities

to reduce contact between people

Administrative

control

• Mandatory use

of non-medical masks

Protection

Effectiveness

Sources: US Centers for Disease Control and Prevention, Centers for Disease Control and Prevention in Guangzhou and Hangzhou, The Johns Hopkins Center for Health Security, the Spanish National Research Council’s Institute of Environmental Assessment and Water Studies (IDAEA-CSIC), European Centre for Disease Prevention and Control, International Laboratory for Air Quality & Health (WHO, Queensland), and the government of South Korea.

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