Why did the Army and Dalgard decide to let the virus burn in the monkey house during the second outbreak instead of going in and euthanizing the monkeys?

Almost a month after the Reston outbreak, the virus reappears at another monkey facility operated by Hazelton Research Products. The C.D.C. and USAMRIID decide to isolate the facility in order to observe the progress of the virus. The virus travels between rooms through the air ducts and effectively kills the entire monkey population. As before, there are no human casualties. Even an animal caretaker named John Coleus who cuts himself with a contaminated scalpel ends up showing no symptoms of the virus. The USAMRIID later discovers that all four caretakers at the original Reston facility test positive for Ebola Reston. However, the strain is symptomless in humans.