1956 Punta Gorda outbreak

1956 Punta Gorda outbreak: In the spring of 1956, at least 150 cases of an illness diagnosed as Epidemic Neuromyasthenia occurred in Punta Gorda, Florida, a small community of approximately 3000 residents on Charlotte Harbor Bay on the state's southwest coast.

Two approaches were applied to determine the nature and incidence of the illness. One consisted of a detailed examination, history and laboratory results of twenty one of the cases reported to physicians. The second approach consisted of a house-to-house survey to identify cases not reported because of a more mild illness presentation.

Symptoms were protean and differed slightly from patient-to-patient. They included but were not limited to: fatigue, headache, nuchal (nape or back of the neck) pain, muscle aches and pain, paraesthesia, fever, nausea and vomiting, diarrhea, loss of appetite, difficulty in swallowing, cognitive and emotional changes, such as mental confusion, memory impairments, especially in short term memory, difficulty with math calculations, depression, episodic crying, "tension," nightmares, hyperventilation, visual disturbances, such as blurred and /or double vision, dizziness, and unsteadiness. The illness course was prolonged and relapsing, often requiring being bedridden, sometimes requiring hospitalization.

Clinical laboratory findings of serum, cerebrospinal fluid, stool, throat swabs, tissue samples, and EKG were interpreted to be unremarkable or within normal range. Many potential causes for the outbreak were investigated, such as, food, milk, water, personal care products, mosquitoes, but none were found.

A mass conversion reaction was ruled out as "little apprehension about the medical problem appeared to exist among the general population."

Outbreak by statistics

 * ~150 cases (6.1% of the community population) were identified
 * the onset of cases occurred from mid-March 1956 until June 1, 1956
 * no children under 12 yrs became ill
 * the incidence and severity was higher in females (~8% of the female population versus ~4% of the male)
 * 42% of medical and hospital staff were affected which is disproportionately higher than the general population
 * the incubation period  of was less  than  one  week,  probably  five  to  six  days