Option 1: AIDS is not caused by a bacterial pathogen. It is caused by the human immunodeficiency virus (HIV), which is a viral pathogen. HIV attacks the immune system, specifically the CD4 cells, and weakens the body`s ability to fight off infections and diseases.

Option 2: Dengue fever is not caused by a bacterial pathogen. It is caused by the dengue virus, which is a viral pathogen. Dengue fever is transmitted through the bite of infected Aedes mosquitoes and usually causes flu-like symptoms, including fever, headache, joint and muscle pain, and rash.

Option 3: COVID-19 is not caused by a bacterial pathogen. It is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is a viral pathogen. COVID-19 is primarily transmitted through respiratory droplets when an infected person coughs, sneezes, talks, or breathes.

Option 4: Typhoid fever is caused by a bacterial pathogen. It is caused by the bacteria called Salmonella typhi. Typhoid fever is usually contracted through contaminated food or water and causes symptoms such as high fever, headache, stomach pain, weakness, and loss of appetite