Final answer:
Patients with infectious diseases commonly experience a fever or mild gastrointestinal issues, with symptoms arising from the rapid multiplication of pathogens within the host's body.
Step-by-step explanation:
Most patients with infectious diseases will have a fever of unexplained origin or mild gastrointestinal problems. When a microorganism infects a host, it can trigger a rapid onset of symptoms, characteristic of an acute disease. Diseases like influenza exhibit an incubation period that is relatively short, and symptoms appear quickly.
On the other hand, certain infectious diseases can persist over the long term, becoming chronic conditions, such as AIDS. Moreover, some diseases can be asymptomatic, presenting no noticeable signs or symptoms initially. Gastrointestinal issues, often associated with infectious diseases, can include symptoms such as diarrhea, vomiting, and abdominal discomfort.