evidence: For the past several decades, intravenous vitamin C has been used as a treatment for multiple types of viral infections.[92] Intravenous vitamin C's effectiveness as an antiviral treatment is likely due to its immune system-enhancing capabilities. In addition, some studies have observed that in critically ill patients such as those with viral infections, sepsis, or accidental injury, plasma levels of vitamin C might be less than 25 percent of those observed in healthy people.[93] [94] [95] [...] Vitamin C also interferes with the replication of viral particles. One in vitro study showed that human immunodeficiency virus type 1-infected cells that were incubated for four days with 150 micrograms per milliliter of vitamin C decreased reverse transcriptase activity by 99 percent and p24 antigen levels by 13 percent (parameters of virus production) compared to untreated cells.[171] Another in vitro study demonstrated a dose-dependent effect of vitamin C to kill influenza viruses, with a vitamin C concentration of 2.5 millimoles per liter eliminating 90 percent of the virus present and a concentration of 20 millimoles per liter fully impeding viral replication.[107]