While there may be a lay tendency to underestimate the 1918 flu, perhaps thinking the impact of the pandemic pales in comparison to the Great War, historians, epidemiologists, demographers, virologists, public health professionals and a variety of other academic specialists continue to dedicate their attention to the 1918 flu.

The 1918-1920 influenza pandemic was remarkable for several reasons. As you mentioned, mortality rate was unusually high (estimated to be 10-20% of those infected with the virus), and the mortality profile differed from normal flu outbreaks. Typically we see a U-shaped age-specific mortality curve with the disproportionate number of flu-related deaths occurring with the very young and very old. The mortality curve for the 1918 influenza pandemic was W-shaped with an unusual spike in the young adult range, and pregnant women were hit unusually hard (Barry 2005). The specifics of why the age-specific mortality differed during the 1918 flu are outside my area of specialty, but may relate to an over-active immune reaction to the virus in healthy young adults, and immunity from a previous influenza epidemic for older adults.

Not all deaths were from the virus itself. Many of the rapid-onset fatalities occurred due to consolidation as the influenza virus triggered fluid infiltration into the lungs, and quickly progressed to pneumonia. Barry mentions healthy-looking individuals boarding a train, then sickening and dying within hours. Cases with longer duration usually saw co-infection with bacterial pneumonia, and in some cases permanent neurological changes from the viral infection itself. Early attempts at finding the causative agent for the epidemic were confounded by the bacterial co-infection, and several prominent researchers at the time continued to hold the misnamed bacteria H. influenzae as the cause of the pandemic.

In 1997 samples of the 1918 influenza virus were recovered from human remains buried in Brevig Mission, Alaska. Other tissue samples were also recovered from the archives of several laboratories, and analyzed in an effort to better understand the specifics of the 1918 influenza strain. Again, the specifics of this viral research are outside my area of expertise but check out the CDC's 1918 Influenza FAQ if you are interested.

In addition to the viral genetic research, other areas of research into the 1918 influenza pandemic focus on a variety of issues like the demographic response to 1918 flu or the effectiveness/ineffectiveness of public health measures during the epidemic.