As early as 1949, research was indicating that extracts of
black tea could inhibit the multiplication of influenza virus.1 Since then, there have been other antiviral reports that have zeroed in on tea polyphenols, including a Chinese paper published in 1992 finding that
green tea inhibits the activities of a wide variety of viruses.2 But over the last 50 years, theories about the mechanisms involved have been scant or insubstantial, and have retarded progress in the branch of virology that specializes in influenza.
Fortunately, the strain of influenza A virus subtype H1N1 responsible for the deaths of up to 50 million people during the Spanish flu pandemic in 1918 was reconstructed in 2005. To achieve this breakthrough, sequence data were pieced together from preserved tissue samples of flu victims, following which viable virus was then synthesized. The 2009 flu H1N1 pandemic involves another strain of influenza A H1N1, commonly known as “swine flu.”
And now, new evidence is starting to lend more plausibility to tea/virus/influenza findings, showing that certain compounds found in tea, and especially in green tea, are able to inhibit an enzyme that is crucial for influenza replication, survival, and spread.
Can you guess what these compounds are? They are catechins . . . polyphenolic antioxidant plant metabolites. Of these, the one with greatest significance is epigallocatechin gallate (EGCG), a catechin long associated with a wide variety of health benefits.
For example, “Human epidemiological and new animal data suggest that tea drinking may decrease the incidence of dementia [Alzheimer’s disease], and Parkinson’s disease. … [due to] the multimodal activities of green tea polyphenols with emphasis on their iron chelating, neurorescue/neuroregenerative and mitochondrial stabilization action.” 
