Infections contracted at a healthcare facility are known as healthcare-associated infections or HAIs. For example, surgical site infection. HAIs also include work-related infections among healthcare staff. HAIs incubate after forty-eight hours of hospitalization and up to thirty days after discharge. The source of HAIs may be exogenous or endogenous. Exogenous infections occur when a pathogen enters a patient's body from their environment, for example, inadvertently spread from contact with a contaminated surface. In contrast, in endogenous infections, the body's normal flora of microorganisms may become pathogenic. It usually occurs when the host is susceptible due to a lowered immune system from illness or treatment. For example, overuse of antibiotics alters the balance of normal flora by causing a reduction in microbial diversity. It can also select for antimicrobial-resistant strains, and make the body more susceptible to infection. Patients may be susceptible to iatrogenic infections caused by certain diagnostics or treatments. For example, using a urinary catheter over an extended period increases the risk of catheter-associated urinary tract infections.