Despite good access to effective antibiotics, Streptococcus pneumoniae (pneumococci) is still a major cause of disease and death in both developing and developed countries. Pneumococci are the main cause of bacterial respiratory tract infections, such as pneumonia, middle ear infection, and sinusitis, in all age groups.
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.