Is leukemia a bacterial or viral?

Answer 1

Viral. Excerpted from Wikipedia, Leukemia:

"Adult T-cell leukemia is caused by human T-lymphotropic virus (HTLV), a virus similar to HIV.

Among adults, the known causes are natural and artificial ionizing radiation, a few viruses such as Human T-lymphotropic virus, and some chemicals, notably benzene and alkylating chemotherapy agents for previous malignancies. Use of tobacco is associated with a small increase in the risk of developing acute myeloid leukemia in adults. Cohort and case-control studies have linked exposure to some petrochemicals and hair dyes to the development of some forms of leukemia. A few cases of maternal-fetal transmission have been reported.[16] Diet has very limited or no effect, although eating more vegetables may confer a small protective benefit.

Viruses have also been linked to some forms of leukemia. Experiments on mice and other mammals have demonstrated the relevance of retroviruses in leukemia, and human retroviruses have also been identified. The first human retrovirus identified was Human T-lymphotropic virus, or HTLV-1, is known to cause adult T-cell leukemia."