HCV | 28% of an IPF cohort had evidence of prior HCV compared with 3.6% of controls [8] | The lack of a coherent signal across studies suggests that HCV is unlikely to be an important trigger for the development of IPF |
Incidence of IPF higher in cohort of HCV positive individuals compared to cohort with HBV [9] |
No association between IPF and HCV [10] |
Association of HCV with a range of non-fibrotic respiratory conditions [11] |
TTV | Lower survival rate in IPF patients with presence of TTV-DNA in serum compared to IPF with no TTV-DNA [12] | Link to pathogenesis unclear. May cause progression of disease or be linked to the development of acute exacerbations |
Detected in BAL during IPF exacerbation and in individuals with acute lung injury [13] |
HHV | 12 out of 13 IPF patients seropositive for EBV [14] | Some conflicting evidence but potential role of HHVs as a co-factor in the initiation and progression of IPF |
Increased EBV in lung biopsy samples and BAL from individuals with IPF compared with controls [15–17] |
At least one HHV detected in 97% of IPF patients compared with 36% controls [18, 19]. |
MHV triggers and enhances fibrotic response in mice [20–23] |