Seattle cancer patients possibly exposed to tuberculosis

This scanning electron micrograph (SEM) depicts some of the ultrastructural details seen in the cell wall configuration of a number of Gram-positive Mycobacterium tuberculosis bacteria. (CDC.gov)

Officials say about 140 cancer patients in Seattle may have been exposed to tuberculosis by a health care worker who tested positive for the disease.

The worker was exposed to patients at University of Washington Medical Center and Seattle Cancer Care Alliance between February and July.

The Seattle and King County Department of Health is sending letters to those who are affected and offered them testing at no charge

Nearly 50 staff members who worked closely to the infected worker have been tested, and all results have come back negative for the disease.

The worker is on medical leave and undergoing treatment.

Tuberculosis is a disease caused by bacteria that are spread from person to person through the air. Symptoms include cough, fever, night sweats and weight loss.