The genus Haemophilus contains significant genetic diversity.Species of the genus Haemophilus require 
protoporphyrin IX (a metabolic intermediate of the hemin biosynthetic pathway),
Epidemiology
As presented in Table 1, except for Haemophilus ducreyi, Haemophilus spp.referred to as X factor and V factor, nicotine adenine dinucleotide (NAD), or nicotine adenine 
dinucleotide phosphate (NADP) for in vitro growth.