Free help with homework

Why join Brainly?

  • ask questions about your assignment
  • get answers with explanations
  • find similar questions


In 1933, researchers discovered that viruses (influenza virus types A, B, and rarely C) cause influenza (flu). Prior to 1933, a bacterium named Haemophilus influenzae was thought to cause the flu. In 1938, Jonas Salk and Thomas Francis developed the first vaccine against flu viruses.
0 0 0
The Brain
  • The Brain
  • Helper
Not sure about the answer?
Learn more with Brainly!
Having trouble with your homework?
Get free help!
  • 80% of questions are answered in under 10 minutes
  • Answers come with explanations, so that you can learn
  • Answer quality is ensured by our experts