Narrative:

While in cruise flight, on IFR flight plan from cxl to bfl, pilot became ill. Symptoms: headache, malaise, cramp. Requested lower altitude. Controller advised MEA 10000 ft, offered 8000 ft temporarily. By this time, PIC was losing peripheral vision. Declared emergency and requested vectors to nearest airport. Vectored to ont via immediate descent and 360 degree turn over OM. Regained full vision at about 6000 ft just before entering a thin, broken cloud layer. Landed without further incident on runway 26L. Unable to stand after parking aircraft. Taken by ambulance to hospital. Diagnosis was acute gastroenteritis (intestinal flu) complicated by altitude. Passenger (PIC's wife) who is an M.D. Concurs and developed intestinal symptoms about 24 hours later. Probable cause: consumption of food in mexico for 3 days prior to flight. Consulted flight surgeon, who agrees. PIC had experienced minor diarrhea in the morning before departure. Took immodium, which cleared symptoms -- probably masking onset of gastric flu. Such apparently minor early symptoms can lead to later trouble -- including increased susceptibility to oxygen want at otherwise safe altitude. PIC recommends pilots returning from mexico be alert for such symptoms, and if at all possible carry oxygen, even though not planning high altitude flight.

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Original NASA ASRS Text

Title: INST RATED PVT PLT DECLARED AN EMER AND LANDED AT THE NEAREST ARPT DURING AN IFR FLT DUE TO PHYSICAL INCAPACITATION.

Narrative: WHILE IN CRUISE FLT, ON IFR FLT PLAN FROM CXL TO BFL, PLT BECAME ILL. SYMPTOMS: HEADACHE, MALAISE, CRAMP. REQUESTED LOWER ALT. CTLR ADVISED MEA 10000 FT, OFFERED 8000 FT TEMPORARILY. BY THIS TIME, PIC WAS LOSING PERIPHERAL VISION. DECLARED EMER AND REQUESTED VECTORS TO NEAREST ARPT. VECTORED TO ONT VIA IMMEDIATE DSCNT AND 360 DEG TURN OVER OM. REGAINED FULL VISION AT ABOUT 6000 FT JUST BEFORE ENTERING A THIN, BROKEN CLOUD LAYER. LANDED WITHOUT FURTHER INCIDENT ON RWY 26L. UNABLE TO STAND AFTER PARKING ACFT. TAKEN BY AMBULANCE TO HOSPITAL. DIAGNOSIS WAS ACUTE GASTROENTERITIS (INTESTINAL FLU) COMPLICATED BY ALT. PAX (PIC'S WIFE) WHO IS AN M.D. CONCURS AND DEVELOPED INTESTINAL SYMPTOMS ABOUT 24 HRS LATER. PROBABLE CAUSE: CONSUMPTION OF FOOD IN MEXICO FOR 3 DAYS PRIOR TO FLT. CONSULTED FLT SURGEON, WHO AGREES. PIC HAD EXPERIENCED MINOR DIARRHEA IN THE MORNING BEFORE DEP. TOOK IMMODIUM, WHICH CLRED SYMPTOMS -- PROBABLY MASKING ONSET OF GASTRIC FLU. SUCH APPARENTLY MINOR EARLY SYMPTOMS CAN LEAD TO LATER TROUBLE -- INCLUDING INCREASED SUSCEPTIBILITY TO OXYGEN WANT AT OTHERWISE SAFE ALT. PIC RECOMMENDS PLTS RETURNING FROM MEXICO BE ALERT FOR SUCH SYMPTOMS, AND IF AT ALL POSSIBLE CARRY OXYGEN, EVEN THOUGH NOT PLANNING HIGH ALT FLT.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.