In one case in Changsha, Hunan Province, he did not wear a mask
0.5 meters away from the infected news
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According to the changsha novel coronavirus pneumonia prevention and control headquarters office released the news, the confirmed case Jiang xxx on March 16 and the foreign confirmed case Xia xxx (confirmed on March 17) in an outdoor public place had a brief time and space intersection, Xia xxx and Jiang xxx did not wear masks, the two walked in opposite directions, passing shoulder to shoulder, about 0.5 meters apart.
Can a distance of about 0.5 meters cause transmission?
Experts said that the answer is yes, Xia Moumou was diagnosed on March 17, when it was already in the detoxification period, people coughing, spitting, or sneezing in the process, the droplets sprayed out of the body are large and small, large particles of droplets will directly settle to the ground, and some small particles of droplets will be suspended in the air, others can cause transmission if inhaled. At this time, Jiang Moumou did not wear a mask and was infected.
Let's take a closer look, if you want to be infected, you need to meet at least the following conditions:
The new coronavirus discharged is still active for a short period of time;
Horizontal distance, virus-containing droplets can spread to case B;
At vertical distances, case B can inhale virus-containing droplets.
It is not difficult at all to achieve the above three conditions.
Let's look at the first point first
It is no problem for the new coronavirus to survive in the aerosol for 3 hours. In the report, case A spits a mouthful of sputum, and case B inhales droplets, but the interval of a few seconds, although not a laboratory condition, can keep the virus active for such a short time.
Look at the first and the first point
Take a look at a study on the distance of cough and droplet transmission:
(1) When there is no wind
Droplets from coughing quickly sink to the ground and spread horizontally for no more than 1 meter.
(2) When the wind speed is 4km/h (about 1 m/s).
Droplets can travel horizontally for 6 meters in just 5 seconds, and the vertical height limit is about 1.63 meters. (Note: The height of the breathing belt of mainland people is generally 0.5 meters -1.5 meters)
(3) When the wind speed is 15km/h (about 4m/s).
Droplets can travel horizontally up to 6 meters in just 1.6 seconds, and the vertical height can be greater than 1.63 meters.
Here's what to say:
In general, coughing discharges droplets only through coughing.
Spitting not only exhales droplets due to the action of clearing phlegm, but also produces a large number of droplets during the process of spitting.
The report mentioned that the wind level in Changsha on the day of contact was three levels of southeast wind.
The corresponding wind speed of the three stages is 3.4-5.4 m/s.
At this wind speed, the droplets produced by spitting are spread within the height range of most people's respiratory bands.
In summary, spitting up a mouthful of phlegm but being infected, it seems mysterious, but in fact, it hides the inevitability in the accident.
In fact, the virus will soon settle to the ground, as long as the mask is worn correctly, the risk of infection can be greatly reduced.
Experts said that no matter how the new crown virus mutates, it is still spread through droplets, contact and other ways, in order to prevent virus infection, standardized wearing masks, frequent hand washing, hand disinfection, and maintaining a safe distance are the most cost-effective and simplest means of protection.
Experts remind: epidemic prevention and control, everyone has the responsibility. Everyone is the first responsible person for their own health, in daily life, we must adhere to the standard of wearing masks, wash hands frequently, maintain 1 meter social distance in public places, consciously do a good job of personal protection, enter public places to take the initiative to cooperate with the sweeping of epidemic prevention "place code", and actively cooperate with epidemic prevention and control measures. Minimize gatherings of people.
Source: Youth Shandong, Shanghai Disease Control
Editor: Ren Mileage Reviewer: Xiao Ran