Which one of the following is caused by a bacterial pathogen?

Typhoid fever is caused by the bacterial pathogen Salmonella typhi [2]. It is classified as a communicable disease that spreads through contaminated food and water [2]. In contrast, the other options are caused by viral pathogens. AIDS (Acquired Immuno Deficiency Syndrome) is caused by the Human Immunodeficiency Virus (HIV), which attacks the immune system [4]. Dengue fever is a mosquito-borne viral disease caused by the dengue virus (DENV), transmitted primarily by the Aedes aegypti mosquito [5]. COVID-19 is caused by the SARS-CoV-2 virus, a highly contagious respiratory pathogen [5]. While all four are infectious diseases, only typhoid fever is listed under bacterial infections, whereas AIDS, Dengue, and COVID-19 are consistently categorized as viral infections.

Sources

1. [1] https://pubmed.ncbi.nlm.nih.gov/34976449/
2. [2] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 3: Health: The Ultimate Treasure > Non-communicable > p. 32
3. [4] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 8: Natural Hazards and Disaster Management > AIDs/HIVs > p. 80
4. [3] https://health.ri.gov/infectious-diseases
5. [5] https://ncvbdc.mohfw.gov.in/Doc/National%20Guidelines%20for%20Clinical%20Management%20of%20Dengue%20Fever%202023.pdf