The Bill and Melinda Gates Foundation's Improving Global Health Program focuses on working on solutions to urgent health challenges in the developing world.
In general, they accept LOIs in the following areas, however, there are specific instances when they will only accept RFPs.
Priority Diseases and Conditions
Acute diarrheal illness
Acute lower respiratory infections
Child health
HIV/AIDS
Malaria
Malnutrition and undernutrition
Reproductive and Maternal Health
Tuberculosis
Vaccine Preventable Diseases
The foundation also supports efforts to address diseases that have a lower overall burden than those noted above, but still have a disproportionate impact in the developing world.
Sexually Transmitted Infections: Gonorrhea, syphilis, and Chlamydia
Kinetoplastid Diseases: Human African trypanosomiasis, visceral leishmaniasis, and Chagas Disease.
Cervical cancer caused by human papillomavirus
Other diseases: Meningitis, dengue, Japanese encephalitis, and trachoma.
To apply for a grant from the Gates Foundation you must first complete their online LOI. You will be asked to attach a 4 page narrative form. You will be notified of a decision in approximately six weeks. LOIs are reviewed on a continuous basis throughout the year.