This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Virology, Subject name: Microbiology
Which influenza strain was isolated in 1989 spreading to many other countries? 
Select and explain. 
A. H2N2, B. H1N1, C. H3N2, D. H5N1
B: H1N1
Answer: B: H1N1 
Explanation: In 1989, epidemic - the reappearance of swine HINI virus Influenza can occur sporadically, as epidemics or pandemics In 2009, H1N1 Epidemic occurred in Mexico-recent Ref: Baveja 5th ed Pg: 468