This study is testing a new drug called CDI-988 to see if it can help healthy adults avoid getting sick from a virus called the Snow Mountain Virus, which is similar to norovirus. Participants will take either the new drug or a placebo (a harmless pill with no medicine) without knowing which one they have. The study lasts for 5 days after participants are given the virus. Researchers will track how much virus is in stool samples and monitor side effects. They will also measure how much CDI-988 is in the blood, a process known as pharmacokinetics.

• Participants should be healthy adults aged 18 to 49 years.
• The study involves 5 days of taking medication and monitoring.
• Participants must not have had recent gastrointestinal issues or norovirus exposure.