Calicivirus is a group of viruses that can infect various animals, including humans. In humans, it is most commonly associated with the norovirus, which causes gastroenteritis, leading to symptoms like vomiting and diarrhea. Caliciviruses are small, round viruses that are resistant to many common disinfectants, making them easily spread in crowded environments. In animals, calicivirus can affect species such as cats, where it causes feline calicivirus (FCV), leading to respiratory issues and oral ulcers. Vaccines are available for FCV to help protect cats from severe illness. Overall, caliciviruses are significant pathogens in both human and animal health.