Macacine alphaherpesvirus 1, also known as herpes B virus (BV), is an alphaherpesvirus endemic to several macaque species, capable of causing zoonotic infections in humans, with high mortality rates. Evidence of reactivation in humans has rarely been reported. Here we depict a case of BV reactivation after 54 years, leading to severe meningoencephalitis. This case supports the use of antiviral prophylaxis in patients surviving a confirmed BV central nervous system infection. We sequenced DNA from BV obtained from the patient's cerebrospinal fluid. Phylogenetic analysis showed significant divergence in the clustering of this particular BV strain compared with other known BVs. Therefore, additional efforts are needed to obtain a broader sequence landscape from BVs circulating in monkeys.