Here is some info on Tyzzer's disease as it affects gerbils but it can also affect hamsters. I know of one breeder who lost nearly her whole hamstery a number of years ago to this disease.
Tyzzer's Disease
Also quoting from the last section there are other infections spread by mice which can infect humans too
It is important to remember that whilst Tyzzer's disease is a common cause of illness in rodents there are other conditions like Listeria, Salmonella and E. coli which can also cause serious illness and death. In many cases the symptoms of these can be similar and they should be dealt with in a similar way. These diseases have an important difference from Tyzzer's disease. All of them are potentially very dangerous for humans and can be fatal to young, ill or elderly people. For this reason no illness of rodents should be treated in a cavalier way. If disease appears it is important to review husbandry practices, treat infected animals if appropriate and to ensure that all sources of illness are destroyed or sterilised.