However, since he does not have fever, it is unlikely your husband has that type of infection. Chemotherapy,
and radiation therapy are the other causes. Other common causes of low WBC are flu, lupus, Hodgkin's lymphoma, some types of cancer, typhoid, malaria, tuberculosis, dengue, enlarged spleen or hyper-spleenism, and folate deficiency. Please discuss with his treating doctor to run tests to find the cause. If all these are ruled out, then it can be bone-marrow suppression.
Take care!