Final answer:
Swollen lymph nodes occur as the immune system responds to fight an infection. In the case of infectious mononucleosis, the Epstein-Barr virus causes an increase in lymphocyte activity, leading to enlarged lymph nodes. Persistent swelling may require a biopsy to rule out other conditions like lymphoma.
Step-by-step explanation:
A nurse's appropriate response to a client with infectious mononucleosis asking why lymph nodes are enlarged is: "Lymph nodes can become swollen when your body is fighting an infection. In your case, the infection causing mononucleosis is likely to be caused by Epstein-Barr virus (EBV), which specifically targets lymphocytes that are found within the lymph nodes. This causes the lymph nodes to swell as they increase in activity to fight off the virus."
It's important to understand that while swollen lymph nodes are commonly due to infections like mononucleosis, they can also be caused by other conditions like lymphoma or reactions to certain medications. A biopsy is often required when swelling persists to rule out conditions such as lymphoma, as was the case with another patient, Wei, mentioned in your materials.