Abstract
Human endogenous retroviruses (HERVs) are virus-related sequences that are a normal part of the human genome; they account for about 8% of the human genome. Reactivation of these ancestral proviral sequences can lead to the generation of functional products. Several reactivated HERVs are associated with cancer and autoimmune diseases. Emerging research suggests that reactivated HERVs may play a significant role in the development of viral diseases such as acquired immune deficiency syndrome (AIDS) and coronavirus disease 2019 (COVID-19), as well as in neuroinflammatory diseases possibly triggered by viral factors, such as multiple sclerosis (MS). Studies exploring the relationship between HERVs and exogenous viral infections have the potential to offer a fresh perspective on developing treatment and prevention strategies for exogenous viral infections. The mechanism of the transactivation of HERVs caused by exogenous viral infection, as well as the contribution of HERVs to viral diseases or diseases triggered by viral factors, deserve further research. Here, we review the relationship between exogenous viruses and HERVs in several common diseases caused or triggered by viral infections, with a focus on the value of HERVs as biomarkers for forecasting disease advancement or prognosis and as potential targets for therapeutic interventions.