In the Shadow Of Blackbirds by Cat Winters

It's 1918 in San Diego, influenza has become an epidemic.  Schools and public buildings are closed.  Citizens wear masks and try home remedies but the death toll climbs.  WWI rages in Europe, taking the young men.  Mary tries to adhere to her scientific principles, until the voice of a beloved childhood friend turned soldier speaks to her  - even though he is dead.

The setting of this story really comes alive through details like clothing and food.  The desperation and sadness of the time are very clear.  The story doesn't really resolve, and some of the characters are not developed, but this is still an interesting book worth reading.