Epstein-Barrr virus (EBV) and cytomegalovirus (CMV) are widespread pathogens that share the characteristic ability of herpesviruses to remain latent within the body over long periods. In mice, the control of herpesviruses replication have also been reported to be associated with the arrest of lung fibrosis [146] . EBV is present in all populations, infecting more than 95% of individuals within the first decades of life. Infection by CMV is reported in 60% of individuals aged 6 and older and more than 90% of aged individuals have antibodies against CMV. In addition, CMV is also the virus most frequently transmitted to a developing fetus. Most healthy people who are infected by EBV and CMV after birth have no symptoms, but infection is important to certain high-risk groups of infants and immunocompromised individuals. Several studies in the adult literature have reported an increased incidence of EBV and CMV infection in patients with pulmonary fibrosis, associated with virus DNA-positive lung tissue biopsies in several cases [147] . However, so far, no evidence of causal relationship between viruses and pulmonary fibrosis has been provided.