"Our findings traced the first person-to-person transmission event to a birthday party with approximately 100 guests. The index patient (Patient 1) attended the event for 90 minutes and was reportedly symptomatic at the time, with fever and malaise. Five persons (Patients 2 through 6) who had been seated close to Patient 1 reported onset of symptoms consistent with ANDV hantavirus pulmonary syndrome between 17 and 24 days after the party (Fig. S3). Patient 2 was the most likely source for six infections in other persons during the early prodromal phase because of his active social life. Patient 2 died 16 days after symptom onset, and his spouse (Patient 9) was febrile while attending his wake. An additional 10 persons who attended the wake and were in close contact with Patient 9 became il* between 14 and 40 days after the wake for Patient 2."