Mystery Illness Outbreak in Lake Tahoe


The Donner Cross located outside of Truckee High School.


Although myalgic encephalomyelitis is a disease that is often associated with Europe, the first two reported clusters of what seem to have been outbreaks of the illness occurred in the United States. These included an outbreak of “atypical poliomyelitis” at a Los Angeles hospital in 1934 and an outbreak of “encephalitis” at a convent in Fond du Lac, Wisconsin, in 1936.

More than a dozen additional illness clusters occurred in the U.S. over the next forty years. One of the best-studied was in 1975, when an outbreak of what was called “infectious venulitis” occurred among more than 50 employees of the Mercy San Juan Hospital in Sacramento, California.

In 1980, physicians in the San Francisco Bay Area began to note a number of cases of illness consistent with the literature on M.E., and other physicians in California, Massachusetts and other places in the U.S. also observed patients with some symptoms of the disease in members of their patient populations. The cases were written up in the literature under the names “chronic Epstein-Barr” or “chronic mononucleosis” rather than as M.E. cases, however.

During the second half of 1984, Dr. Paul Cheney and Dr. Daniel Peterson began seeing cases matching the illness description in their practice in Incline Village, Nevada.

Ultimately a few hundred cases from the Lake Tahoe-Truckee area were recorded by the doctors. Many of these patients experienced even more severe symptoms (especially in terms of neurological problems) than had individuals in previous epidemics.

As was the case in the Royal Free epidemic in London in the 1950’s and in many of the other epidemics, a large number of individuals in the Lake Tahoe epidemic became acutely sick with a flu-like illness. A few of these individuals died from the flu-like illness; many individuals had their condition become chronic; and some experienced apparent recovery.

Although specific symptoms varied a bit across patients and over time, the presentation was fairly similar across sufferers and in many cases was very severe. Epidemic survivor Erik Johnson described the illness as follows:

Marathon runners, overnight, could not climb a flight of stairs. People who set out in the morning for work had to be carried home. Those who could still drive got lost trying to find their way home. A math teacher could not do addition. An English teacher could not conjugate a sentence.

Throats looked like people had gargled with battery acid. We could hardly stand without leaning on something. Walking was more like lurching: aim for the door, and those with this illness only made it through fifty percent of the time. Those who closed their eyes dropped instantly. People suffered from malnutrition in the midst of a fully stocked kitchen because they couldn’t stand long enough or think well enough to prepare food. 

Reading was out of the question. If you tried, you’d find that you were reading the same paragraph over and over again. TV caused seizures. Lights in the room burned our eyes. Music hurt our heads.

We were like soldiers coming out of a war zone. We lay comatose, but it wasn’t sleep. When we dragged ourselves back into consciousness, it was in groggy, toxic, “Twilight Zone” fashion.

I can still remember the sense of panic the first time I told my arm to reach for something and nothing happened. I remember saying things, and having everyone in the room tell me that I was speaking in tongues. I could have sworn that I was speaking perfect English. Other times, I told people to speak clearly, because it seemed they were speaking Greek. 

This was not fatigue. It seemed to me more like a stroke victim who struggles, but cannot find the words to speak and cannot move.


As was the case in previous epidemics (including the L.A. County Hospital outbreak in 1934 and the London Royal Free Hospital outbreak in 1955), many of the Tahoe cases were clustered among individuals working or attending school in particular buildings.

Some of these included Truckee High School, North Tahoe High School, and the Hyatt Regency Hotel & Casino in Incline Village. Many of the affected employees complained about the buildings feeling toxic and having a moldy smell.

In a journal paper published about a decade later, researchers Alexander Chester and  Paul Levine discussed their observation that the sick building syndrome issues present in certain buildings (including Truckee High School) seemed to be related to occupants being more likely to come down with “chronic fatigue syndrome.”

The Tahoe-Truckee cohort was the subject of extensive study by many prestigious researchers during the time period from 1985-1990. Their findings revealed many similarities with AIDS (a disease that also had emerged in 1980 in the San Francisco Bay Area and then quickly spread to other areas of the U.S.).

Like AIDS patients, affected individuals from the Tahoe epidemic suffered from low natural killer cell activity and resultant runaway reactivation of various herpesviruses, including EBV, CMV and what is now called HHV-6A. Also like AIDS patients, the Tahoe patients had many small plaques (dubbed “unidentified bright objects”) evident in MRI brain scans.

Other abnormalities recorded in the Tahoe cohort included unusually high helper/suppressor T-cell ratios; large amounts of Rnase-L/RNA ribosomal destruction; highly elevated Interleukin-2 levels; and unusually low erythrocyte sedimentation rates (0, 1 or 2 in many patients).

Most but not all of the Tahoe patients had the reactivated Epstein-Barr virus described in the papers on “chronic EBV,” thus suggesting that this particular virus was not the underlying cause of the disease.

Physicians considered to be experts in the disease of M.E., including Dr. Byron Hyde, diagnosed patients in the Tahoe epidemic as having the disease.

In mid-1985, two researchers from the CDC – Dr. Gary Holmes and Dr. Jon Kaplan – visited the Lake Tahoe area in order to investigate the epidemic. In 1987, they wrote up a few observations from their visit in an article published in JAMA.

Because the Lake Tahoe epidemic was so severe and located in a wealthy tourist area, it received a great deal of nationwide publicity, including coverage by The New York Times, the major national TV news networks, and the TV show “20/20.”

The Incline Village doctors were then contacted by thousands of patients throughout the U.S. suffering from symptoms typical of the disease, and many more patients joined support organizations. Physician David Bell, M.D., reported a cluster outbreak among children in Lyndonville, NY, and a number of other new cluster outbreaks were reported as well.

In 1987, Nevada Senator Harry Reid spoke out on the importance of devoting resources to the topic of figuring out what had happened in the Lake Tahoe epidemic.

Also in 1987, the CDC created a task force headed by the CDC researchers who had visited Lake Tahoe, Gary Holmes and Jon Kaplan. In 1988, the task force released a consensus definition providing a set of very broad criteria for an illness that they called “the chronic fatigue syndrome.” Their rationale for choosing a new name was that since not all sufferers of the illness were positive for Epstein-Barr virus, the name “chronic EBV” was inappropriate.

Although literature on myalgic encephalomyelitis had been mentioned in the 1987 paper produced by Gary Holmes and Jon Kaplan, neither M.E. nor the previous literature related to it was referenced in the 1988 paper.

In 1992, a team of 17 researchers who had studied the Lake Tahoe outbreak published a paper summarizing findings from the outbreak in the Annals of Internal Medicine. The paper focused on three abnormalities found in the patients: 1) high CD4/CD8 T-cell ratios, 2) MRI scans showing “punctate, subcortical areas of high signal intensity consistent with edema or demyelination,” and c) active replication of HHV-6. The article did not refer to either M.E. or CFS, and instead described the cohort as having “a chronic debilitating illness of acute onset.” The lead author on the paper was Anthony Komaroff of Harvard University; among the co-authors was Robert Gallo, a researcher widely known for his role in the discovery of the HIV virus several years earlier.

In response, three representatives from the Centers for Disease Control wrote a letter to the publication criticizing the research methodology and stating, “We conclude that the disease Buchwald and coworkers described is not the chronic fatigue syndrome or any other clinical entity and that they showed no association with HHV-6 replication.”

The CDC then spent the next 15 years funding research that focused on only mildly ill individuals and that suggested that psychological factors and stress were responsible for the condition that it was continuing to call “chronic fatigue syndrome.”

The Fukuda criteria (which broadened the definition of the illness even beyond the one stated in the Holmes 1988 paper) were put forth by the CDC in 1994.

Several different histories describe in great detail the ways in which the CDC and other government agencies approached the disease during this time, arguing that they had made a purposeful effort to draw attention away from it and to minimize its importance. These accounts include the article “CFS and the CDC: A Long, Tangled Tale” by David Tuller; the book Osler’s Web by Hillary Johnson; and the monograph Thirty Years of Disdain by Mary Dimmock and Matthew Lazell-Fairman.

Starting in 2014, the Department of Health and Human Services (DHHS) and the National Institutes of Health (NIH) began bringing up M.E. in their discussions of CFS, often using the term “ME/CFS.”

The CDC has continued to refer to the disease as just “CFS” with no mention of M.E., and to include only the broad Fukuda criteria on its website, however.

-Lisa Petrison, Ph.D.


Read more about the Lake Tahoe outbreak.

Lake Tahoe Epidemic Information Resources


Read more about the 1985 outbreak in Lyndonville.

The Puzzle of Chronic Fatigue


Read more about the 1975 Sacramento outbreak.

An Outbreak at Mercy San Juan Hospital in Sacramento, California


Read about other M.E. outbreaks.

Cluster Outbreaks


A segment on the Lake Tahoe epidemic ran on ABC-TV’s “Prime Time Live” in 1996. 


Information on this website is presented by Paradigm Change. Links are in orange (no underlining).