Clara Mass was an American nurse. She was born in 1876 at East Orange, New Jersey and died in 1901 at Havana, Cuba of yellow fever. She was the only woman and the only American to die during the yellow fever experiments of 1900 to 1901. After graduating from the Newark German Hospital School of Nursing in 1895 she volunteered to serve as a contract nurse with the U.S. Army Medical Department at the outbreak of the Spanish-American war of 1898. During her first term of service she worked at army camps in Florida, Georgia, and Cuba. She volunteered again in 1900 and was sent first to the Philippines and then back to Cuba, where at the Las AnimasHospital in Havana, she volunteered to take part in an experiment conducted by Major William C Gorgas and John Guiteras on yellow fever immunization. The experiment involved her being infected with the disease, from which she promptly died ten days later. Research Clara Mass