A cluster of eight people in North Seattle, described as heterosexuals, drug users, and recently homeless, has been diagnosed with HIV infections since February, and health officials are worried that their cases could represent a new pattern of transmission for a virus that has been in steep decline.
Officials suspect that changes in drug use are to blame.
“There could be a large outbreak potentially,” said Dr. Jeff Duchin, health officer for Public Health-Seattle and King County. “There may be a large number of people vulnerable to new HIV infections, which would be a very big problem.”
The diagnoses are among 19 HIV cases reported so far this year among heterosexuals in King County. For all of last year, that number was seven, according to the health agency. It has averaged 10 for the past decade.
Gay and bisexual men are most at risk to contract HIV in Washington state. Statewide, 461 cases were diagnosed each year from 2012-2016, on average, according to state Department of Health statistics. Of those cases, an average of 290 each year were among gay and bisexual men.
The recent Seattle cluster is a departure from the typical pattern of infection, and particularly concerning because it involves homeless people who might not have access to health care or might be missed by HIV-prevention services.
“I would see this cluster as being the canary in the coal mine but not cause for panic,” said Dr. Peter Shalit, a primary care physician in private practice who has been treating HIV patients since the 1990s. “It just sort of reminds us that the epidemic is not over and it’s going to pop up in places that we’re not paying attention to with our prevention efforts.”
That so many more heterosexuals in King County have been diagnosed with the virus this year suggests HIV might be spreading between different populations.
“We’ve known for a while that men who have sex with men who inject methamphetamine have a very high rate of HIV infection over 40 percent,” Duchin said.
In contrast, other groups of injective drug users, including heterosexuals, have rates of about 1 to 3 percent, he said.
Duchin said interactions between populations of heroin users and men who have sex with men and use methamphetamine could explain the recent increase in cases.
The recent HIV cluster was discovered through a monitoring program. Medical providers statewide must notify officials when a patient is diagnosed with HIV. After a diagnosis, local public health officials try to get the patient into medical care and determine if others were at risk.
“You try to identify the social milieu and all the people in that area, test them,” Shalit said. “Get them on treatment as soon as possible. If they’re on effective treatment, they can’t transmit.”
Duchin said transmission links among four of the eight people of this cluster have been identified. He said investigators had not tied a specific location to the HIV transmission, other than North Seattle.
At least half of the people in the cluster are receiving medical care. Duchin said health officials are working to make sure syringe-exchange and condom programs are meeting demand. The local health department also is increasing testing and outreach to homeless people.
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