"I recently traveled with my two dogs that are vaccinated. I stayed with a friend who had a ten-month old dog that was not vaccinated. After we were there for two days, her dog got sick and died from Parvo. Could my dogs carry the virus from stopovers at roadside rest areas and given it to her dog? This was a very sad situation and I need to know if it was because of my visit."
This is a sad situation and there is no definite way to "prove" how the unvaccinated dog became ill with parvo, but since he became ill so quickly after the visiting dogs arrival, it is unlikely that they were the source. On average, the incubation period for canine parvovirus (CPV) is 3-7 days. If the non-vaccinated dog became sick and died within 2 days of the visitor's arrival, it would be unlikely that the visiting dogs brought in the virus.
Parvovirus is a hardy virus and is considered to be ubiquitous, meaning that it is potentially everywhere. An unvaccinated dog is at high risk for parvo and other diseases from many possible sources. Vaccination for this disease is the best prevention.
Adult vaccinated dogs are well-protected against parvo. Their immune systems mount a response against any parvovirus they may come in contact with, preventing clinical illness.
Parvovirus in the Environment
Dogs infected with parvovirus shed millions of viral particles with each diarrhea bowel movement and may shed virus for 2-3 weeks post-exposure. Canine parvovirus survives in the environment and on surfaces. Disinfecting the environment of parvo is difficult, and this virus may last a few weeks, months, or even up to 2 years, if the conditions are favorable. Sunlight and low humidity (arid) conditions will inactivate the virus quicker than cool, moist, shady conditions. Water, via rain showers or a hose, will dilute the amount of infective viral particles, but not inactivate the virus.
In addition to virus-laden fecal matter and environmental contamination, parvovirus can be transmitted via surfaces - hands, tools, bowls, shoes, other pets, clothing, etc. A dilute bleach solution (1 part bleach to 30 parts water) should be used on "cleanable" surfaces, good sanitation and hand-washing for non-bleachable surfaces. (Never use bleach on pets!)
It is impossible to know for sure, but it is likely that the unvaccinated dog was exposed/incubating the virus prior to the traveling dogs arrival. The fact that the visiting dogs are adults and vaccinated helped protect them from contracting the parvovirus during their stay.