In winter months, passengers onboard cruise ships run a far higher risk of contracting a virus than summer travelers. 

The Diamond Princess is currently being quarantined in Japan because of the coronavirus, scientists analyzed almost 120 serious virus outbreaks aboard cruise ships over the past decade. All of them are recorded by the US Centers for Disease Control. Any ship that stops at the US and which has an outbreak of gastrointestinal illness aboard must report it to the Centers for Disease Control.