SEATTLE - The Seattle-King County Health Department says tests have confirmed four men have forms of HIV that are highly resistant to drugs.

One was tested in 2005 and the other three last year, but recently researchers identified a link between all four.

The cluster is a concern to health officials because this HIV is difficult to treat.

The public health officer, Dorothy Teeter, says officials are stepping up the monitoring for HIV drug resistance in the Seattle area.

HIV-AIDS program director Doctor Bob Wood says this news is a message to men to practice safe sex.

Health workers are trying to contact the sex partners of the four men to test them for HIV. The department says all four men had a history of methamphetamine use and sex with multiple, mostly anonymous, male sex partners.