Bacteria are biological agents of which some cause diseases such as typhoid, cholera, tuberculosis, pertussis, etc.
While some are helpful to humans, for example, some bacteria live in the small intestine and help in the digestion of food.
Bacteria multiply faster in warm conditions. Therefore, it is advised to keep food in the refrigerator to avoid spoiling in summers due to bacterial infestation, which ultimately leads to causing diseases.
Final answer: Bacteria multiply faster in warm conditions.