with the epsilon4 allele of the gene APOE. HSV-1 appears to be particularly damaging to the nervous system and increases one's risk of developing Alzheimer's disease. The virus interacts with the components and receptors of lipoproteins, which may lead to the development of Alzheimer's disease. This research identifies HSVs as the pathogen most clearly linked to the establishment of Alzheimer's. According to a study done in 1997, without the presence of the gene allele, HSV-1 does not appear to cause any neurological damage or increase the risk of Alzheimer's. However, a more recent prospective study published in 2008 with a cohort of 591 people showed a statistically significant difference between patients with antibodies indicating recent reactivation of HSV and those without these antibodies in the incidence of Alzheimer's disease, without direct correlation to the APOE-epsilon4 allele. The trial had a small sample of patients who did not have the antibody at baseline, so the results should be viewed as highly uncertain. In 2011, Manchester University scientists showed that treating HSV1-infected cells with antiviral agents decreased the accumulation of β-amyloid and tau protein and also decreased HSV-1 replication. A 2018 retrospective study from Taiwan on 33,000 patients found that being infected with herpes simplex virus increased the risk of dementia 2.56 times (95% CI: 2.3-2.8) in patients not receiving anti-herpetic medications (2.6 times for HSV-1 infections and 2.0 times for HSV-2 infections). However, HSV-infected patients who were receiving anti-herpetic medications (acyclovir, famciclovir, ganciclovir, idoxuridine, penciclovir, tromantadine, valaciclovir, or valganciclovir) showed no elevated risk of dementia compared to patients uninfected with HSV. Multiplicity reactivation Multiplicity reactivation (MR) is the process by which viral genomes containing inactivating damage interact within an infected cell to form a viable viral genome. MR was originally discovered with the bacterial virus bacteriophage T4, but was subsequently also found with pathogenic viruses including influenza virus, HIV-1, adenovirus simian virus 40, vaccinia virus, reovirus, poliovirus and herpes simplex virus. When HSV particles are exposed to doses of a DNA damaging agent that would be lethal in single infections, but are then allowed to undergo multiple infection (i.e. two or more viruses per host cell), MR is observed. Enhanced survival of HSV-1 due to MR occurs upon exposure to different DNA damaging agents, including methyl methanesulfonate, trimethylpsoralen (which causes inter-strand DNA cross-links), and UV light. After treatment of genetically marked HSV with trimethylpsoralen, recombination between the marked viruses increases, suggesting