An Undiscovered Coronavirus? The Mystery of the ‘Russian Flu’

Gina Kolata: “H1N1 came back after being gone for two decades. It and another virus, H3N2, have been circulating ever since. ‘Until 1977, we never had two subtypes circulating at the same time,’ Dr. Monto said. ‘We don’t understand why one subtype pushed out the other and why it didn’t happen in 1977.’”