"Noma is a rapidly progressive, polymicrobial, opportunistic infection that occurs during periods of compromised immune function. Fusobacterium necrophorum and Prevotella intermedia are thought to be key players in the process and interact with one or more other bacterial organisms (such as Borrelia vincentii, Porphyromonas gingivalis, Tannerella forsynthesis, Treponema denticola, Staphylococcus aureus, and nonhemolytic Streptococcus spp).

The reported predisposing factors include:
Malnutrition or dehydration
Poor oral hygiene
Poor sanitation
Unsafe drinking water
Proximity to unkempt livestock
Recent illness
Malignancy
An immunodeficiency disorder, including AIDS

Noma was observed in Nazi concentration camps in World War II, and was studied by Nazi physician Josef Mengele. In many cases a recent debilitating illness, usually measles and sometimes herpes simplex, varicella (chicken pox), scarlet fever, malaria, tuberculosis, gastroenteritis or bronchopneumonia, precedes the appearance of noma as well as cancers such as leukemia. In many instances the infection begins as necrotizing ulcerative gingivitis (NUG). Early presentation is unclear as noma is often well progressed at initial presentation.

Noma, unlike most infections, is able to spread through anatomic barriers such as muscle.

In the developed world, noma has virtually disappeared except for an occasional case related to immunosuppressive conditions such as HIV infection, severe combined immunodeficiency syndrome, or intense immunosuppressive therapy. The World Health Organization (WHO) estimates the global yearly incidence to be approximately 140,000, of which 100,000 are between 1 and 7 years old and living in sub-Saharan Africa."
STOLEN FROM http://en.wikipedia.org/wiki/Noma_%28disease%29 :P