Which condition is caused by a bacterial infection?

Strep throat is a condition specifically caused by a bacterial infection, primarily due to the bacteria Streptococcus pyogenes, also known as group A Streptococcus. This pathogen can lead to inflammation and infection of the throat, resulting in symptoms such as sore throat, fever, and swollen lymph nodes.

In contrast, the flu is caused by influenza viruses, making it a viral respiratory illness. The common cold is also caused by viruses, most commonly rhinoviruses. COVID-19 is caused by the coronavirus SARS-CoV-2, which is another type of viral infection. Thus, strep throat is distinct among these options as it arises from a bacterial origin, highlighting the importance of recognizing different infectious agents and their associated diseases in clinical practice.