THE PLAGUE OF THE SPANISH LADY
by RICHARD COLLIER 376 pages. Atheneum. $10.
This recounting of the worldwide influenza epidemic of 1918-19 not only appears in time for the season's first sniffles but also in the wake of what might be called the new hypochondria. Two famous mastectomies, plus frightening books and articles about heart attacks and the cancer-causing properties of such common substances as asbestos and spray-can propellants have added to our usual anxieties. Yet as millions of people over 60 will recall, for real drenching fear nothing tops an old-fashioned plague.