What’s the difference between influenza A and influenza B, and does it matter which you catch?
Each fall, the flu emerges as a formidable force, spreading through the droplets produced when people cough, sneeze or talk, and sometimes hitching a ride to our noses by way of the infected surfaces that we touch. Influenza viruses cause tens of millions of illnesses and thousands of deaths in the United States each year.
There are two players every flu season: influenza Type A and Type B. Influenza A tends to pop up early in the season and accounts for more than 75 percent of all cases, while influenza B typically has a distinct but much smaller peak in late February or March.
“You tend to have one or the other virus predominant at any given time,” said Anice Lowen, an associate professor of microbiology and immunology at the Emory University School of Medicine. Here’s what to know about the flu viruses.
What’s the difference between Type A and Type B?
Influenza A viruses come in many varieties. Four subtypes commonly affect humans, Dr. Lowen said — you may have heard of H1N1, for example. But many more influenza A viruses have been identified in animals, which makes it a potential source of pandemics whenever a new type of influenza A jumps to humans, she said. All four flu pandemics — in 1918, 1957 and 1968 and the swine flu pandemic of 2009 — were caused by Type A viruses.