Mrs. Izquierdo is described as a Crazy Cat Lady by the other residents of the building, but we never see her cats. However, she was the first of the infected. Maybe she killed and/or ate her cats.
It's easy to miss because of the great sound design, but while Manu and the rest are carrying the senior cop down the stairs, you can hear the screams of Mrs. Izquierdo before Alex falls to his death.
Fridge Brilliance
Most people are possessed within seconds of being infected, but not Jennifer the young girl who was said to be ill for hours before succumbing. The religious background of the infection explains the discrepancy: Children Are Innocent thus take longer to possess than any of the adults who certainly have a fair share of sins to speak of.
Once Angela and Pablo come out and look for Manu, they find out he has been infected. Although it is briefly shown you can see Manu with his mouth full of blood after smashing the head of the Japanese Woman. Since the virus is spread through bodily fluids, this is probably why he got infected.
