A cell culture hood is being used to study the lymphocytic choriomeningitis virus (LCMV) outbreak in tamarind monkeys. Monkey cells are being cultured in cell culture flasks. Syringes are shown attached to filters that would allow the isolation of viruses. A zoom-in window on the flask reveals cells that are at late stages of LCMV infection. In the second zoom-in window on the cells, a new viral particle is shown budding off a cell (right). In order to isolate the viruses from monkey samples in this image, a filter is being used. Explain how this technique would provide a pure sample of virus to study..