Some harmful bacteria can cause diseases like tetanus, salmonellosis, conjunctivitis, and sometimes pneumonia and tonsillitis. Viruses can also cause diseases in humans such as measles, chickenpox, the flu, colds, papilloma, and AIDS. Infectious diseases spread from person to person through the air or contaminated food or through mosquito bites in the case of malaria. Maintaining a healthy lifestyle includes eating five small meals per day, drinking water, exercising, sleeping enough, getting checkups and vaccinations, avoiding excessive screen time and saying no to drugs.