The most sensitive period in raising dairy calves is from birth to 3 mo of age. The most prevalent causes of morbidity and mortality from birth to weaning are scours and pneumonia, with 75% of calf deaths occurring due to these illnesses. Scours, or diarrhea, is a common illness in young dairy calves, accounting for approximately 50 to 75% of calf death during the first 3 weeks of life. The most common causes of calf scours are bacteria, viruses, and protozoa. Treatment of scours requires identification of the causative organism so that the proper intervention plan can be selected. It is important to note that many organisms that cause scours are zoonotic, so individuals caring for these animals must be extremely conscientious. Antibiotics are most useful when bacteria are the causative agent. Salmonella Heidelberg is a bacterium that causes severe illness in calves and humans. Calves infected with Salmonella Heidelberg may develop diarrhea or die abruptly without any clinical signs. People can also become infected with Salmonella Heidelberg with symptoms including diarrhea, fever, and abdominal cramps, which may last 4 to 7 d. From January 2015 through November 2017, a multi-drug-resistant Salmonella Heidelberg was linked to contact with dairy calves. A total of 56 people in 15 states were infected with this organism. Surveillance in veterinary diagnostic laboratories showed that calves in several states were infected with the outbreak strains of multidrug-resistant Salmonella Heidelberg, and a CDC investigation showed that the clinical isolates from affected individuals were resistant to multiple antibiotics. Currently, no approved antimicrobial drugs are effective against the Salmonella Heidelberg strains isolated from calves. Since periodic occurrence of Salmonella Heidelberg continues to be of concern, proper sanitation and hygiene are of utmost importance in preventing scours in calves and protecting human health.