Influenza A virus appeared first in October of 1997. A activity then seemed to steadily increase, peak in January, then slowly decline through April. A total of 285 samples grew influenza A virus. Last season, influenza B was first isolated in our laboratory late in December and slowly increased over the next several months. A total of 30 samples grew influenza B virus, last season.
Influenza viruses are notorious for their seasonality.
In temperate climates such as ours, increased activity occurs mostly in winter months. This increased influenza activity may be in the form of a local outbreak, a nationwide epidemic, or a global pandemic. Although the virus was first isolated in 1933, historical records suggest influenza epidemics have occurred every 1 to 3 years for several centuries. The greatest pandemic, of course, occurred in 1918, in which over 20 million peopled died worldwide, over half a million of whom were in the United States. You may copy or post this newsletter.