Neuromyasthenia and Chronic Fatigue Syndrome : A Ten-Year Follow-Up

Neuromyasthenia and Chronic Fatigue Syndrome in Northern Nevada/California: A Ten-Year Follow-Up of an Outbreak

Journal: J of Chronic Fatigue Syndrome, Vol. 9(3/4) 2001, pp. 3-14

Author Affiliations: Paula S. Strickland is a former graduate student at George Washington University, School of Public Health and Health Services,

Washington, DC. Paul H. Levine is affiliated with the Viral Epidemiology Branch, National Cancer Institute, Bethesda, MD and George Washington University, School of Public Health and Health Services, Washington, DC. Daniel L. Petersen is Internal Medicine Physician, and Karen O’Brien is

Technician, Sierra Internal Medicine Associates, Incline Village, NV.

Thomas Fears is Statistician, National Cancer Institute, Bethesda, MD.

Address correspondence to: Paul H. Levine, MD, George Washington

University, School of Public Health and Health Services, Washington, DC

20037 (E-mail: ).

The authors are very grateful to George Reed, Ph.D., for his assistance in

data analysis, and Deborah Pilkington for assistance in reviewing charts.


In 1984-87, an outbreak of debilitating fatigue was reported by two

physicians in the private practice of internal medicine in Incline

Village, Nevada. Follow-up questionnaires were sent in 1995 to the 259

patients in this outbreak. The results were analyzed to determine how

many patients met the latest Centers for Disease Control and Prevention

(CDC) case definition for Chronic Fatigue Syndrome (CFS), Idiopathic

Chronic Fatigue (ICF), or Prolonged Fatigue (PF). Data were analyzed

separately for those living in the Lake Tahoe area and those referred

from other locales. Of those returning questionnaires (123/259), 41 % met

the CDC case definition for CFS, 56% met the criteria for inclusion in

the subgroup ICF, and 3% experienced PF. In the population-based Lake

Tahoe group, symptomatic women were more likely to have CFS than ICF

whereas symptomatic men were likely to fit ICF criteria. Also in this

group, full recovery was reported more often among Lake Tahoe

participants classified as having ICF (43%) than participants classified

as having CFS (15%).


In 1984, two internal medicine practitioners noted an apparent outbreak

of fatiguing illness in Northern Nevada/California, which subsequently

became the subject of several reports (1-4). Although often referred to

as an outbreak of chronic fatigue syndrome (CFS), most of the studies

which evaluated 259 patients in this cluster between 1984 and 1987 were

carried out prior to the first published CFS working definition in 1988

(5), and it has not been clear what proportion of the patients who

suffered from the fatiguing illness actually had CFS. In a ten-year

follow-up to the study of Buchwald et al. (3), investigators involved

with the Incline Village private practice prepared a questionnaire that

was mailed in March 1995 to the 259 patients included in this report.

The questionnaire was initially designed to identify CFS patients based

on the case definition described by Holmes et al. in 1988 (5). However,

since this case definition does not provide a strategy for subgrouping

cases of chronic fatigue which are not CFS, the CFS definition and

chronic fatigue subgroups described by Fukuda et al. in 1994 (6) were

used in this report. Utilizing the questionnaire data our study had four

objectives: first, to summarize the questionnaire data using descriptive

information in order to determine what proportion of the affected

patients in the Northern Nevada/California cluster met the latest case

definition of CFS (6); second, to determine what proportion met the

criteria of the subgrouping described by Fukuda et al. (6); third, to

determine what proportion of the patients have recovered from their

illness after approximately ten years, and fourth, to determine if our

earlier data suggesting a relationship between this outbreak and the

subsequent increased incidence of brain tumors and non-Hodgkin’s lymphoma

(7) would be confirmed in this cohort.


The CFS definitions and subgroups of chronic fatigue used to categorize

participants were based on the categories described by Fukuda et al. (6).

Chronic Fatigue Syndrome: Participants were classified as having CFS if

they experienced severe fatigue that persisted or relapsed for six months

or more, which was of new or definite onset; was not substantially

alleviated by rest, and resulted in substantial reduction in activities.

They also had to have four or more CFS associated symptoms (impaired

memory or concentration, sore throat, tender cervical or axillary lymph

nodes, muscle pain, multi-joint pain, new headaches, unrefreshing sleep,

and postexertional malaise). Finally, their illness could not be

attributed to any of a group of specific organic or psychiatric

conditions known to be associated with fatigue.

Idiopathic Chronic Fatigue: Participants were classified as having

Idiopathic Chronic Fatigue (ICF) if they experienced significant fatigue

which persisted for six months or longer, but the severity of fatigue or

the symptoms associated with fatigue did not meet the CFS definition.

Prolonged Fatigue: Participants were classified as having Prolonged

Fatigue (PF) if they experienced fatigue that was severe enough to seek

medical attention, but the duration of the fatigue was less than six


Patients were also characterized geographically to distinguish those in

the proximate area of the outbreak versus those subsequently referred

because of the interest of the physicians in chronic fatigue. The “Tahoe

group” is defined as those persons who were non-referral patients and

residents of the Lake Tahoe/Incline Village areas at the time of initial


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© 2001 by The Haworth Press, Inc. All rights reserved.

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