Francisella novicida is a bacterium of the Francisellaceae family, which consist of Gram-negative pathogenic bacteria.

[3] Though F. novicida is considered a rare pathogen, its close relative F. tularensis is well known for causing tularemia.

Unlike F. tularensis, there have been no documented cases of F. novicida or F. novicida-like strain transmission to humans through arthropod bites.

Results of DNA-DNA hybridization and genome sequencing experiments indicate F. novicida is genetically close to F. tularensis.

Human or animal infections with F. t. novicida are very rare and few publications describe it, in part because it is infrequently isolated.

[5] For medically important organisms such as Francisella, clear guidelines exist for differentiation of subspecies.

This means the strains of a single species may differ in 20-25% of their genome without affecting their taxonomic status.

While all of this supports F. novicida to be classified as a subspecies, many still believe enough evidence exists to create a separate species.

The immunological differences, though, are the strongest evidence used to support the idea that F. novicida and F. tularensis are separate species.

[6] Therefore, a fundamental difference appears to exist in the antigenic composition of the two organisms, which was also demonstrated by cross-absorption in passive cutaneous anaphylaxis test (PCAs).