"There is no contagion, no hama and no serpent in a hungry belly. However, the possessor of sick livestock must not stop at the same place as the possessor of healthy livestock, but the possessor of healthy livestock may stop wherever he wishes."

They said, "Messenger of Allah, Why is that?" The Messenger of Allah, may Allah bless him and grant him peace, said, "It is harmful."

Note: The majority of scholars interpret this to mean that these things in and of themselves do not transmit or cause harm through supernatural or hidden means but that Allah is ultimately in control and any fearful superstition around these is false.