The most common cause of leukopenia is viral infections, along with some severe bacterial infections. Common symptoms of viral and bacterial infections include dizziness, headache, nausea, vomiting, chills, fever, cough, expectoration, abdominal pain, diarrhea, urgent urination, and frequent urination. Generally, further examinations can be conducted through blood draws and routine tests of blood, urine, and stool cultures. If there is an accompanying hematological disease, such as thrombocytopenia, symptoms can include general weakness, body aches, and bone pain; further bone marrow examinations should be conducted.