NEW YORK (Reuters Health) - British investigators describe 20 cases of humans being infected with Mycobacterium bovis, a type of tuberculosis normally confined to cattle. In six instances, the outbreak appears to have resulted from person-to-person transmission.

This report "emphasizes the need to maintain control measures for human and bovine tuberculosis," Dr. Jason T. Evans, from the West Midlands Public Health Laboratory in Birmingham, UK, and colleagues note in The Lancet medical journal. "Transmission and subsequent disease was probably due to a combination of host and environmental factors."

The researchers performed DNA fingerprinting of all tuberculosis cases that arose in central England between 2001 and 2005. Of the 20 cases that were due to M. bovis, a cluster of six were genetically identical.

All six cases involved young, UK-born individuals, the report indicates. The infection involved the lungs in five patients and caused meningitis in one patient, who died.

The patients had shared social links through bars in two areas. The lack of contact with animals or dairy consumption in all but one of the individuals helped make the case for person-to-person transmission of the infection.

In a related editorial, Dr. Charles O. Thoen, from Iowa State University in Ames, and Dr. Philip A. LoBue, from the Centers for Disease Control and Prevention in Atlanta, comment that "investigations are needed to elucidate the relative importance of M. bovis in the worldwide tuberculosis problem in human beings, especially in developing countries."

Special focus should be paid to countries with widespread HIV infection, since it raises the risk of M. bovis infection, they add.