This is how viruses are distributed when breathing.
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Keeping distance is the order of the day. If the air conditioners are turned on, this should be even bigger, according to the new study.
A study published in the journal “Emerging Infectious Diseases” shows what consequences this can have and what role too little clearance and running air conditioning play. In this, the authors around Jianyun Lu from the health authority in Guangzhou trace how an asymptomatic patient infected ten other people during lunch at a restaurant visit on January 24, 2020.
One visit to the restaurant, ten new infections
The infected, named by researchers A1, was eating out with four family members (A2-A5). The recently traveled group from Wuhan to the Chinese city of Guangzhou sat at the middle of three tables. Two other families were placed at the other two tables (B and C). All three tables were in the airflow from the same air conditioner.
As Lu and his colleagues write, A1 developed the first symptoms on the same day: with a fever and cough, he went to the hospital and was diagnosed with Covid-19. In the days after the restaurant visit, his four companions fell ill, as did three members of the B family and two members of the C family.
The remaining 73 guests of the restaurant, on the other hand, remained healthy. According to the researchers, they had not been sitting in the airflow from the air conditioning system. The company’s eight employees were also subsequently tested negative for Covid-19.
Classic droplet infection excluded
According to the Lu team, this abnormality indicates that the air conditioning system, in whose air flow the three families were sitting, was involved. He had first poured over the table of family C, then over that of the family of the patient, before finally reaching the table of family B. Apparently the air was then sucked back in by the air conditioner. There is no other explanation for why not only members of family B fell ill, but also members of family C, according to the researchers.
Another point in favor of contributing, says the researchers: “Virus transmission cannot be explained by droplet transmission alone.” The prerequisite for this is that the other person is in close proximity. Otherwise, the droplets would sink to the bottom due to their weight.
Types of transmission
The rapid spread of the novel corona virus continues to puzzle scientists. There are three types of transmission:
Droplet infection:In such a case, the pathogen comes into the air when sneezing, coughing, speaking through droplets of saliva and is then inhaled by another person or absorbed through the mucous membranes. It is proven.
Air infection: Pathogens do not attach themselves to droplets, but to aerosols. Due to their small size and light weight, they can last longer in the air. It is unclear whether this is the case with Sars-CoV-2. While some researchers believe it is possible, others assume that Covid-19 pathogens that are so widespread are probably not dosed high enough to cause infections.
Smear infection: In such a case, pathogens are passed on via a chain of touches. These can take place from person to person, but also via objects. This transmission path is also the subject of discussion.
More space in air-conditioned rooms
Since the distances between the tables of families A, B and C were all larger than droplets can fly, this would not be an explanation. “However, the airflow from the air conditioner could have carried the droplets a greater distance than usual.”
In order to prevent Sars-CoV-2 and other pathogens from spreading more widely than usual in air-conditioned rooms, the scientists now recommend increasing the distance between the tables and improving ventilation.
Weakness of the study
Lu and his colleagues point out that it has not been proven that all patients in the restaurant became infected with A1. This could just as well have infected his relatives outside. Similarly, families B and C could initially have infected one person and later passed the virus on to others at home.
However, since the illnesses all occurred around the same time, it cannot be assumed. The researchers consider it certain that A1 has transmitted at least one person to each of the two neighboring tables in the restaurant.
