One case series study [29] revealed that the improvement of MHF severity was related to genetic variation of the polymorphic dinucleotide (CA) repeat of the estrogen receptor beta (ESR2) gene on chromosome 14, which include three types: two short alleles (SS), two long alleles (LL), and a short and long allele (SL) [30,31]. Here, ESR2 is linked to Marburg hemorrhagic fever.