What virus causes a disease similar to smallpox but is less severe?

The disease that is similar to smallpox but less severe is caused by the benign epidermal monkeypox virus. Monkeypox is a zoonotic virus that is part of the Orthopoxvirus genus, which includes the smallpox virus. Although monkeypox can result in symptoms similar to those of smallpox, it generally causes a milder form of the disease with lower mortality rates.

Monkeypox can be transmitted from animals to humans and can also spread between humans. The clinical presentation often resembles that of smallpox, featuring fever, rash, and lymphadenopathy; however, the overall severity is considerably less, making it a distinct entity. This is crucial in understanding how human health is impacted by viruses in the Orthopoxvirus family.

Other options do not pertain to diseases similar to smallpox. Measles is a viral infection characterized by its own specific symptoms, Q fever is another unrelated infectious disease caused by the bacterium Coxiella burnetii, and Newcastle disease virus is associated with avian diseases, particularly in birds.