Histoplasmosis is an infection caused by breathing in spores of a fungus often found in bird and bat droppings. Histoplasmosis is most commonly transmitted when these spores become airborne, often during cleanup or demolition projects. In the United States, histoplasmosis commonly occurs in the Mississippi and Ohio River valleys, though it can occur in other areas, too. Two surveys were done in Biloxi, Mississippi 12 months apart. Of 4,000 people surveyed the first time, 25 already had antibodies to histoplasmosis. Twelve months later, 35 had antibodies, including the original 25. what is The incidence of histoplasmosis during the 12 month period was
a) Infection
b) Breathing
c) Transmission
d) Airborne