My souvenirs of my trip to Brazil last week for Web Summit Rio are no longer limited to my conference badge and a few items of event swag, because it appears that I also imported a case of Covid from that gathering.

My first heads-up that I might have repeated last year’s pattern–go to an event in a new-to-me country, pick up Covid there, test positive at home only after a few days of mild symptoms–came when I got a message Saturday from my fellow Web Summit speaker and Fast Company editor Harry McCracken, saying that he’d just tested positive after feeling some nasal congestion.

I felt a little sneezier than usual myself but tested negative Saturday night. With those cold-like symptoms still around, I tested negative a second time Monday morning. Would the streak persist through a third test Wednesday afternoon? No, reader, it did not.

So just like I did last year, I’m isolating at home from my so-far symptom-free wife and kid (it helps that it’s so nice outside that opening every window is not just doable but desirable) and wondering when symptoms that have reached the annoying end of common-cold severity will fade. And how long it will take me to test negative again.

And like last year, I’m wondering when and where I might have picked up this case. Web Summit’s venue, the Riocentro conference center, had what seemed good ventilation, with doors wide open to the outdoors in every exhibit hall and the speaker lounge. But that was not the case for the Riocentro arena and the shuttle vans in which I spent way too much time in traffic–in where I did not wear a mask.

My thinking, presumably like that of the infectious-disease experts who picked up Covid at a Centers for Disease Control conference last month, was that the risk had ebbed far enough. Covid stats are way down worldwide, and I’ve been vaccinated four times–the two original doses in the spring of 2021, a booster in the fall of 2021, and a bivalent booster last fall–on top of last summer’s case.

But that protection might not be as effective if I ran into a new variant–a subject on which researchers may now have a data point from me, thanks to my spending a few minutes at Dulles after arriving Saturday morning to provide a sample at a CDC genomic-surveillance testing station.

And even if I’d masked up more at Web Summit, that still would have left my time indoors at receptions and dinners. There’s only so much you can do to buy down the risk if you’re going to fly to another continent to speak at a conference drawing 21,000-plus attendees from 91 countries, and I decided upfront that the opportunity justified the risk. On in fewer words: Buy the ticket, take the ride.

Unlike last year, this case of Covid isn’t throwing a wrench into any travel plans. It is, however, icing my Mother’s Day agenda for my wife, and I feel lousy about that.