In 1909, Paul Ehrlich cured a rabbit of the bacterial disease syphilis by injecting it with a compound called Salvarsan. Ehrlich’s concept of the ‘magic bullet’ gained momentum, and the antibiotic era launched, with many bacterial targets sought and hit by newly developed magic bullets such as penicillin and streptomycin.
But antiviral therapy lagged behind. One reason is that viruses were discovered much later than other microbes.
A second is that it was believed that the virus-cell relationship was so close as to preclude effective chemotherapy.
But the realisation that certain steps in the viral replication cycle were virus-specific, prompted interest in how the cycle could be interrupted, and the first breakthrough came in the early 80s with an antiviral agent targeting herpes viruses.
Further advances have occurred with a range of viruses, but especially with hepatitis viruses, HIV and respiratory viruses.
Of the nine human herpes viruses, antiviral drugs have been approved for the treatment of herpes simplex virus types 1 and 2 (HSV-1 and HSV-2), varicella-zoster virus (VZV) and cytomegalovirus (CMV).