Human betaherpesvirus 6B is a species of virus in the genus Roseolovirus, subfamily Betaherpesvirinae, family Herpesviridae, order Herpesvirales. In 1992 the two variants were recognised within Human herpesvirus 6 on the basis of differing restriction endonuclease cleavages, monoclonal antibody reactions, growth patterns. In 2012 these two variants were recognised as distinct species by the International Committee on Taxonomy of Viruses and named Human betaherpesvirus 6A and Human betaherpesvirus 6B. Despite now being recognised as paraphyletic, the name Human herpesvirus 6 still sees usage in clinical contexts. Human betaherpesvirus 6B affects humans. Primary infection with this virus is the cause of the common childhood illness exanthema subitum. Additionally, reactivation is common in transplant recipients, which can cause several clinical manifestations such as encephalitis, bone marrow suppression, pneumonitis
A Will is the eighth album by Japanese rock band Luna Sea, released on December 11, 2013. It is their first album of new material in over thirteen years, as they reunited in 2010 after disbanding in 2000; the album reached number 3 on both Billboard Japan. Commenting on the fact that the band had not created an album in so long, Sugizo stated "Each of us have become accomplished artists on our own, it is more like we are all coming together as solo artists to make a Luna Sea album." He went on to compare A Will and the process of the band recording it to their first album and being a newly formed group. What makes this album special is that it was born from that thought process." The band selected songs by going through those that each member had gathered through the years, writing them while living together. Many songs that did not end up being included on the album were recorded. On the album's name, which Ryuichi suggested, Sugizo explained: "WILL" just by itself is a word in future tense, expressing intent to do something.
It has the nuance of pointing toward the future, although it has a positive meaning, it means that things are at a place where everything could come to an end and there would be no regrets. Speaking of the opening track "Anthem of Light", Sugizo said "These are wild times, but there's no reason to release negative energy just because of that. Additionally, he believes there is no reason for Luna Sea to give a political message, only to create music that will "stimulate our imagination." J feels that "Anthem of Light" is an answer to their earlier song "Into the Sun", that they both have similar rhythms and beats. He wrote "Glowing", which focuses on the "sexiness" of rock music for the current Luna Sea, he remarked that despite it being a simple song, the band worked on it for months."Both "Maria" and "Gin no Tsuki" were first unveiled in 2010 at separate concerts at the Tokyo Dome as part of the band's reunion world tour, although the lyrics and arrangements of both have been reworked and the latter's titled changed from "Days of Repetition".
The album version of "Ran" is different from the single cut. Lead guitarist Sugizo described "Metamorphosis" as a "progressive piece in the form of hardcore/speed metal" where Shinya's drumming shines, likened it to the band's earlier tracks "Fate" and "In Future". J remarked that the string section at the end of the last track "Grace" connects back to the first song on the album. Three limited editions of A Will were produced: Limited Edition A includes the album on high-fidelity SHM-CD, a photobook, a Blu-ray with the music videos for the four single tracks and their TV ads. In commemoration of the album's release, Tower Records in Shibuya hosted a special event from December 5–23, 2013, where the band's instruments, behind the scenes photos, items used in the album's creation were displayed. Never before seen footage and a preview of the album were featured. A Will and the band's other seven major label studio albums were released on vinyl record for the first time on May 29, 2019. All tracks are written by Luna Sea.