What We Know about HV.1 (EG.5.1.6.1) SARS-CoV-2 Variant
Authors: Cobar Oscar , Cobar Stella 
Published: March 2024

Background: HV.1 (EG.5.1.6.1) was the dominant strain in the U.S. as of the end of second week of December 2023, according to the U.S. Centers for Disease Control and Prevention (CDC). The strain is a descendant of EG.5 family that was identified in China in February 2023 and was first detected in the United States in April 2023. 44 mutations in S-protein, 2 in Membrane and Envelope viral structures, 5 mutations in the Nucleocapsid, 21 mutations in Orf1a, 1 mutation in Orf3a, Orf6, Orf10, and 2 mutations in Orf8 virus genome open reading frames are reported. The symptoms of HV.1 are similar that of other Omicron variants, these include fever or chills, cough, shortness of breath or difficulty breathing, fatigue, muscle or body aches, headache, new loss of taste or smell, sore throat, congestion or runny nose, nausea or vomiting, and diarrhea, but congestion, sore throat and dry cough seem to be the three most prominent symptoms right now. Since HV.1 belongs to the same family as XBB, health experts assumethat updated vaccines are expected to be effective against this new dominant subvariant.The only way to distinguish (COVID-19) from RSV and flu, both of which are now gaining steam, is by testing. Aim: The purpose of the manuscript is to present a systematic review on the prevalence, structural, genomic, and pathogenic characteristics of HV.1 from October 1, 2023, as of December 31, 2023, emphasizing on the variant genetic characteristics, contagiousness, and potential pathogenicity. Material and Methods: Original scientific articles published in Medline, Pubmed, Science Direct, Web of Science, Scopus, EBSCO and BioMed Central databases, official health organizations electronic publications, and specialized media in the subject, were electronically searched to accomplish the aim of the study. Articles published in any language were included from October 2023 to present using a variety of keywords in combination. The studies relevant to our review were analysed and compared. Results and Discussion: HV.1 showed significantly lower plasma neutralisation titers compared with their parental strains after acquiring L452R and A475V mutations, explaining their growth advantages. A475V mutation also resulted in decreased binding affinity, enhancing immune evasion compared to HK.3 (XBB.1.5+FLip). However, the L452R mutation of HV.1 did not affect binding affinity. 44 mutations in S-protein, 2 in Membrane and Envelope viral structures, 5 in the Nucleocapsid, 21 in Orf1a, 1 mutation in Orf3a, Orf6, Orf10, and 2 in Orf8 virus genome open reading frames mutations are reported. These mutations give to HV.1 improved ability to enter the human cell, although no greater pathogenicity or severity of the symptoms. Conclusions: The latest data from US-CDC in 2023, shows HV.1 as the second prevalent SARS-CoV-2 variant in the United States. HV.1 (XBB.1.9.2.5.1.6.1 or EG.5.1.6.1) in October 2023, quickly increase its prevalence and surpassed other variants, includingEG.5 (Eris) to become the most prevalent strain in USA until week ending on December 9, 2023. HV.1 has a similar transmission rate, exhibits a greater evasive capacity of immune-generated antibodies than EG.5.1* family of SARS-CoV-2, produce similar symptoms that of other Omicron variants, are expected not to produce an increase in hospitalizations and mortality rate and the SARS-CoV-2 vaccines recently developed by Pfizer and Moderna, must be effective against this Omicron subvariant.For now HV.1 does not seem harmful in terms of creating a deadly disease but is still contagious enough to not be ignored.