Question: This may seem trivial and myopic, but is there any risk of transmission when petting the neighbor’s dog or smelling their roses (which every passer-by does!)?

Answer: When it comes to minimizing risk, the clearest communication I’ve seen is from Japan (Figure 1). We’ve talked about risk many times, but remembering the 3 Cs — Closed spaces, Crowded places, Close-contact settings — is key for understanding which scenarios carry increased risk. There’s not going to be guidance for every type of daily activity — like smelling the roses — so I recommend using the 3 Cs to guide your risk calculation. Passing some fragrant roses? Check the scene. Closed spaces? Crowded places? Close-contact settings? If yes, avoid. If not, enjoy! Here’s a bit more information specific to the two examples you gave:

Smelling the roses: I assume the issue is that other people may have had their faces close up in the blossoms, breathing on the petals, and presumably depositing their germs. I assume these roses are outside, so we can be confident that the virus dies quickly thanks to sun, wind and inhospitable conditions. If the 3 Cs aren’t present, we don’t need to worry about airborne transmission. Instead the worry is fomite transmission — from petal to your face and into your body. This scenario seems exceptionally unlikely. If you have a whiff of concern (see what I did there), make sure you don’t touch the flower with any part of your body, especially your face. If you avoid touching the rose with your nose, you’ll avoid any lingering risk, ever small as it may be.

Petting the puppy: It’s always good, in COVID times and not, to wash your hands after petting an animal. Please be sure to wash your hands after petting the dog. We have no evidence of any dog transmitting the virus to any human, and for more on animals and COVID-19, see CDC’s guidance here.

Finally, one more important point. The risk of fomite transmission in most settings is very low. The virus cannot enter through your healthy skin. So, when we’re talking about fomite transmission, we’re generally talking about this type of scenario: virus particles are on your hands from having touched a germy surface; your hands then touch your mouth, nose, or eyes; the virus enters such an orifice and infects you. Thanks to the wonders of our skin, you don’t need to stop touching things (or petting dogs) — with regard to fomite transmission, as long as you wash your hands well and avoid touching your face after you touch that thing (or that dog), you’re well protected.

Figure 1. Avoid the 3 Cs (from Prime Minister’s Office of Japan)