Although I can't be certain, I suspect we may have been the victims of the norovirus. In any event, I googled some depressing facts (I was trained as an engineer, so obviously this isn't medical advice - this list came mostly from the above link, as well as the CDC and the NYCDOHMH):
- It takes a good 20 seconds of vigorous handwashing to get rid of norovirus.
- Over-the-counter hand sanitizers are mostly ineffective against it.
- Chlorine will kill it in a strong concentration (not diluted in a swimming pool or tap water).
- It survives freezing, and heating up to 140 degrees (water this hot burns within seconds).