TNF and animal viral hepatitis: Similarly, a pegylated version of interferon-alfa 2a, with demonstrated benefit in BS, is also not available in the West for BS.[9] Interferon-alfa 2a has been used successfully in various diseases for which it was licensed.[10] It was also widely used successfully off-license, such as in BS, as it was cheaper and, given the prevalence of chronic infections such as viral hepatitis or mycobacterial diseases in Silk Route countries, where infliximab or other tumor necrosis factor (TNF) inhibitors might be relatively contraindicated, it was a most attractive choice.