Clara Louise Maass was a nurse who contributed to the research on yellow fever at the turn of century. She was working as a civilian nurse in Cuba, where army Majors William Gorgas and Walter Reed were conducting experiments to isolate the cause of the disease. Test ruled out dirt and poor sanitation as cause of yellow fever, and a mosquito was the suspected carrier. Clara was among the group who volunteered to be bitten by the insect. She contracted the disease and died on August 24, 1901. She was the only woman to participate in the experiment and among the few volunteers to die from it. With her death, the study ended; the results of the experiment provided conclusive evidence that mosquitoes were the source of the disease.