What causes pathogens to change?

Pathogens change due to mutations in their genetic material, which can occur during replication. These mutations can be driven by environmental pressures, such as the host's immune response or the use of antibiotics and antiviral medications. Additionally, genetic recombination and reassortment can occur, particularly in viruses, allowing for the exchange of genetic material between different strains. This evolutionary process enables pathogens to adapt and survive, potentially leading to increased virulence or resistance to treatments.