We just went to the vet today, where my guinea pigs' lungs were checked. The vet said they sounded completely clear and fine, so we took them back home and they were/and still are being amazingly active and themselves. However during floortime, one of my piggies sneezed twice hard-sneezes in a row (she was eating hay though, perhaps a bit of dust went in?), and then another more normal sneeze about a minute after. Then a few more minutes after, my other piggie sneezed as well. About ten minutes after, she sneezed for a second time. Keep in mind, she got checked at about 4:00 PM, and this all happened at a bit before 10:00 PM. Could they have gotten a URI this fast? I shall keep an eye on them. They are being very active and eating very well. I do not know if they really could have gotten a URI in six hours?