Are respiratory diseases contagious?

Not all respiratory diseases are contagious. Whether they are contagious depends on the cause of the disease. Only those caused by transmissible pathogens and the pathogens can spread outward through respiratory secretions can cause human-to-human transmission.

Many people subconsciously stay away when they hear the words "respiratory disease". In fact, there is really no need to apply one-size-fits-all. When I was attending a community clinic a while ago, I met a little girl. A colleague in the same department had a common bacterial pharyngitis. She didn't even dare to use the printer that others had touched. She had to spray alcohol on the handed report before she dared to accept it. She was completely over-stressed.

Non-infectious respiratory diseases such as asthma, COPD, and common allergic rhinitis that we often talk about have no involvement of foreign pathogens at all. To put it bluntly, there is an inflammatory reaction or structural damage in the own airways, which is a "problem in one's own body." Even if the other person coughs or sneezes at you, no pathogenic pathogens will be expelled, and there is no contagion at all. Previously, there were rumors on the Internet that "asthma can be transmitted through saliva." This statement has no scientific basis at all.

But if the causative agent is a transmissible microorganism such as a virus, Mycobacterium tuberculosis, or atypical pathogens, then you have to be careful, such as influenza, COVID-19, measles, and active tuberculosis. The pathogens can attach to droplets and aerosols and float in the air. If you are in the same closed space with an infected person, you may be infected even if the small droplets emitted by the other person speaking loudly are inhaled by you. When the influenza broke out at the end of last year, a young nurse in our department did not wear an N95 when she was seeing patients. She talked to a child with high fever for three minutes and her fever reached 39 degrees the next day. When the infection is strong, the disease spreads so quickly.

Of course, there are some intermediate cases, which have been discussed in the academic community, such as common bacterial pneumonia and mild bacterial bronchitis. Healthy adults are generally not infected when exposed to them, but if they are exposed to the elderly, children, or people taking immunosuppressants, there is a certain risk of infection. This is why the respiratory departments of hospitals now require visitors to wear masks, just to block these potential pathogens that pose a threat to vulnerable groups.

In fact, to put it simply, judging whether a respiratory disease is contagious depends on whether its "root cause" is a living pathogen that can escape. If it is your own problem, there is no need to worry. If it is infected by a foreign pathogen, you can basically prevent it by wearing a mask and maintaining social distance. There is no need to kill a whole boat of people with one stroke.