Can you infect someone with vape clouds?

Yes, this is entirely possible. Although most people are more familiar with the chemical hazards of second-hand smoke, the exhaled e-cigarette vapor can indeed serve as a transmission route for infectious diseases. The main transmission route is through the use of contaminated equipment.
☁️ Second-hand smoke: Acting as the "express train" for respiratory viruses
When an infected person uses an e-cigarette, the virus adheres to the exhaled droplets and aerosols, forming a "virus carrier". Moreover, the smoke particles produced by e-cigarettes are extremely tiny (at the sub-micron level), capable of remaining suspended in a confined space for several hours and spreading over a distance of more than 2 meters. This actually may increase the duration of virus presence in the air and the potential range of transmission.
?? Quantifying risks
A 2020 model study quantified the relative increase in infection risk when staying in the same room with an e-cigarette user during their contagious period:
Low-intensity use (for 80-90% of e-cigarette users): Compared to normal breathing, the risk of infection increases by approximately 1%.
High-intensity usage: The risk of infection will increase by 5-17%.
Speaking or coughing (even in non-smoking situations): The risk of infection increases by 40-90% or even more than 200% (for reference).
This kind of transmission mainly occurs through two channels: Direct transmission refers to inhaling the "second-hand smoke" exhaled by the infected person; Indirect transmission means that the virus settles on object surfaces as smoke particles, forming contaminants. When others touch these surfaces and then touch their mouths and noses, they will be infected. The threat can last for several hours to several days. In addition, the chemical substances contained in the e-cigarette aerosol can suppress the immune system and damage the respiratory system, making the inhaler more susceptible to infection.
?? Direct sharing: The risk of "saliva exchange" with shared devices
Apart from inhaling second-hand smoke, another overlooked but more direct risk is sharing e-cigarette devices. This is essentially a high-risk "saliva exchange" behavior that is highly likely to spread diseases through mouth-to-mouth contact, including:
Respiratory viruses: such as influenza, COVID-19, common cold and pneumonia.
Herpes virus: Sharing a damp straw can spread the herpes simplex virus, causing oral herpes.
Infectious mononucleosis: Also known as "the kissing disease", it is highly contagious and can be transmitted through saliva.
Enterovirus: For instance, norovirus can be transmitted through contaminated hands and utensils.
☣️ Other risks: Chemical hazards of the smoke itself
Even if the user is completely healthy, the e-cigarette smoke itself is also a harmful mixture that contains nicotine, ultrafine particles, volatile organic compounds (such as benzene), heavy metals (such as lead), and flavoring chemicals (such as diacetyl). Long-term or high-intensity exposure to these substances increases the risk of various health problems for bystanders (especially infants, pregnant women, and those with respiratory diseases), including cardiovascular diseases, lung cancer, and lung damage.
?? Summary and Recommendations
In summary, the smoke from electronic cigarettes "is not inherently toxic", but it can serve as a transmission medium, significantly expanding the range and efficiency of respiratory virus transmission. At the same time, the smoke from electronic cigarettes also poses chemical hazards.
To protect your own and others' health, you can refer to the following suggestions:
In public places, actively avoid the smoke from e-cigarettes.
Never share the e-cigarette device with anyone.
Complete smoking and e-cigarette bans are implemented both indoors and in vehicles.