On October 4, 1989, a primate quarantine unit in Reston received a shipment of 100 monkeys from a Philippine facility. By November, nearly one-third of the animals had died – a much higher percentage than normal – of mysterious causes. Dan Dalgard, the consulting veterinarian of the unit, was alarmed and contacted the US Army Medical Research Institute (USAMRIID). Dalgard talked to Peter Jahrling, a virologist at USAMRIID, who told him to send a few samples of the dead monkeys. Neither one of them was prepared for what they found.