"I did some more research tonight and found in Eugene Garretts book on page 212, that he found the earliest known distribution of POW cards was Dec 1942 to a "Small Medical Unit left behind at Camp O'Donnell" . That certainly fits with the clues on this card , and the history of the person who sent it. I am fairly certain that Camp 13 in Dec 1942, had to have been Camp O'Donnell."..............Kurt Stauffer

Capt William E. Wilson was an MD and served at Sternberg hospital. He was at O'Donnell and later Cabanatuan. He was later shipped to Japan in 1944 and survived the war. 

I believe this card is from O'Donnell from the time period in @ July 1942 that the Japanese left US Medical Personnell and sick POW's there,  even after the rest of the POW's were sent to Cabanatuan. 

I also have 3 cards from Camp #1, and other ephemera to include his POW ID tag from Japan, medals , and newspaper clippings.

Here is some info from the Provost Marshal Report about O'Donnell:

On 6 July 1942, all the American personnel who were in the prisoner of war enclosure previous to the hospital's arrival, left for Cabanatuan, with the exception of 156 seriously ill patients, 43 officers and men. This same day General Hospital #1 officially opened at Camp O'Donnell and the work of unpacking and setting up another hospital began.

On 19 July 1942, Colonel Duckworth, Captains Le Mire and Keltz, and 52 enlisted men, some of whom were formerly at Little Baguio and Corregidor, arrived, thus bringing the hospital personnel nearer to its proper strength.

By this time sanitary methods were functioning properly. Old latrines and urine soakage pits were covered over and new ones dug. They were burned out daily or sprinkled with lime to kill flies and mosquitos. Stagnant pools of water were drained. The tall grass which grows in abundance in this part of the country was cut and burned to help stamp out the mosquitos. Barracks were repaired and cleaned up. All water for drinking purposes was boiled if possible or chlorinated. Refuse piles and garbage were burned or buried, and a general daily policing of the camp was started.

A definite sign of improvement was noticed throughout the camp, and finally by 20 July, patients were returning to duty to their respective subgroups for the first time. The death rate took a noticeable drop. By 21 July 1942, the daily death rate was below 100. Dispensaries of the small but efficient manner were started in every subgroup, where immediate treatment could be given to all localized cases, Patients returning from the hospitals were given their daily prophylactic dose of quinine. New patients were being admitted to the hospitals as fast as a vacancy occurred. It now became evident that to increase the already high efficiency of the various sections they should be made into General Hospitals, thereby bringing to the minimum all administrative problems and to a maximum of professional and sanitary care of each hospital and subgroup. August I, 1942, was the date set for the change from sections of General Hospital #1 into general hospitals within the hospital center of Camp O'Donnell. On 31 July 1942, therefore, General Hospital #1 ceased to be the parent organization in command and became part of the new hospital center.