Arenaviruses are a type of small virus commonly found in rodents. When a person becomes infected with an arenavirus, symptoms usually begin within 10 days.
Smallpox was a systemic disease, officially eradicated since 1979 (WHO), caused by infection with the Variola major virus, whose only reservoir was infected humans.
The transmission of Clostridioides difficile can be patient-to-patient, via contaminated hands of healthcare workers or by environmental contamination.