Songfacts®:

• "Parasite Eve" originated in 2019 when frontman Oli Sykes read an article about a Japanese superbug that had become heat resistant because of climate change. Borrowing the title from a late 1990s action role-playing video game, he came up with the idea for a horror song about a deadly virus. Bring Me The Horizon started to record the track in February 2020 before COVID-19 really took hold across the globe.
  
  As the pandemic started to sweep worldwide, the band felt the parallels were too similar so set the song aside. "It was really weird," Sykes admitted to NME. "We'd heard about the pandemic in China, but then the similarities between what we were writing about started to become closer to reality. Every time there was a news story about it, we'd turn to each other and say 'Parasite Eve', not realizing the magnitude of it all. We shelved the song for a bit because it felt bit too close to the bone."
  
  Lockdown triggered a writing process that began to align and merge the boundaries between isolation and the virus. As time went on, Sykes and keyboardist Jordan Fish concluded the song applied to the times and that instead of shying from it, they should embrace the dark side. Through a series of video calls and remote recording, they completed "Parasite Eve" and released it as a single on June 26, 2020.
  
  "In our music we've always wanted to escape, but there's been too much escapism and ignoring the problems in the world. It's not what the world needs," Sykes explained to NME. "The world needs more and needs to think about it and remember. You can't just brush over it and expect life to go back to normal, because it f--king ain't. In so many ways, we need to change. That's what rock music is about - addressing the dark side and processing it."
• "Parasite Eve" is the lead single from Post Human, a series of four EPs that when combined make an album. "The idea behind 'Post Human' is looking at how we've stepped out of evolution and the food chain,' explained Sykes. "If we can do that, then we can take responsibility for what we've done to the planet and become something better than what humans are right now."
• Sykes and Fish produced the track with Doom and Doom Eternal composer Mick Gordon. A big fan of the computer game, Sykes reached out to Gordon and asked if he come on board. Once involved, Gordon worked remotely with the Bring Me The Horizon pair to add a cinematic element to the song.
• The song starts off with a sample of Petar Lyondev's Bulgarian folk song "Ergen Deda" performed by the female choir Le Mystère des Voix Bulgares. Translated into English, it reads:
  
  Has put his cap askew, just like this, just like that
  To the one side, to the other side, just like this, just like that
  
  Sykes explained to Kerrang that he'd got into Bulgarian choir music and the history behind it. "In some regions, it's closely linked to ceremonies involving walking over hot coals and they go into this trance," he said. "When I hear vocals like that - maybe because it's sung in different scales and rhythms to Western music - it has this euphoric feeling, but also because it's so foreign to me it has this feeling of panic and chaos. It felt like the perfect way to open a song that is about essentially that."
• Oli Sykes' wife, the Brazilian model and artist Alissa Salls, sang the female vocals.
• The first of the four Post Humans projects, Post Human: Survival Horror, was released digitally on October 30, 2020, peaking at #5 in the UK. When the band made the EP available on vinyl, CD, and cassette three months later, the record returned to the UK albums chart, this time securing the top spot; 92% of Post Human: Survival Horror's chart sales that week were physical purchases. It was Bring Me The Horizon's second UK chart-topper, following their 2019 album Amo.