Study finds airborne risk 1,000 times greater than contact transmission

  Two years have passed, the new crown pneumonia epidemic is still spreading, and the pressure of epidemic prevention is still difficult to reduce.
  Clarifying the transmission mode and infection risk of the virus will help to formulate more scientific prevention and control measures, and is the basis for efficient anti-epidemic.
  Early research suggests that SARS-CoV-2 carriers spread viral particles into the environment. These shed virus particles can survive in the air for hours while remaining infectious; after adhering to a surface, they can even survive for up to 3 days (depending on factors such as temperature, humidity, and surface material), in other words, during this time People are also at high risk of becoming infected if they accidentally touch surfaces contaminated with it.
  The latter is called contact transmission and is currently one of the main ways of new crown infection (the other is droplet transmission). The former is called air transmission. As the third relatively “non-mainstream” transmission method, the risk geometry is still inconclusive in the academic circles.
  Recently, the team of Professor Xi Chuanwu from the University of Michigan published an academic paper in the Journal of Exposure Science and Environmental Epidemiology. The main point of the paper has improved our understanding of airborne transmission, and also subverted our past cognition – the probability of new coronavirus transmission through the air (aerosol) is 1000 times the probability of transmission through the surface of objects.
  The research team sampled and tested the new coronavirus in multiple campus environments, collecting a total of 256 air samples and 517 surface samples.
  The results show that gyms can be extremely dangerous public places during the epidemic. Of all samples collected at the gym, 75% of air samples and 50% of surface samples were positive. Among them, 3/4 of the positive samples came from the water dispenser button in the gym, and none of the fitness equipment was “hit”.
  And the recognized high-risk place – the office, the positive detection rate is actually very low. In addition, computer keyboards, light switches, desks, and desks had lower positive rates. Subsequently, the research team integrated the data model to assess the risk of people being infected with the new crown at different positive sites. The results showed that the risk of inhalation infection varied according to the length of exposure, but overall the risk of inhalation infection was much greater than the risk of infection following surface contact. The probability of contracting the new crown due to exposure to airborne virus particles is about 1% (about one infection per 100 air contacts), and the probability of becoming ill due to contact with surface viruses is about 1 in 100,000 (only one infection per 100,000 surface contacts) ).
  Taking the campus gym as an example, when the virus concentration in the air is 0.06gc/L (slightly lower than the average concentration of this air sampling), if the exerciser does not wear a mask and performs 40 minutes of medium and high-intensity training, inhaling the infected The risk is about 1.5%. When a single hand touches the contaminated surface (equal to the average concentration of the surface sampling), and the hand is still in contact with the mucous membrane, the risk of infection is only 1/100,000. Although co-author Professor Richard Neitzel believes that the results of this study of regularly sanitized campuses are not representative of all community settings, he also believes that people should pay more attention to airborne transmission of the new coronavirus than contact transmission.
  Since airborne transmission is so dangerous, how can we prevent it?
  The paper pointed out that if a room is ventilated 10 times per hour to ensure 36% of the air circulation, the risk of infection can be reduced by 87%; regardless of the ventilation, wearing N95 masks can reduce the risk of infection by 38.1% to 98.5%.
  It can be seen that ensuring air circulation and wearing masks correctly are still two major epidemic prevention tools.

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