Complex sentence: In April 2009 a novel flu strain evolved that combined genes from human, pig, and bird flu, initially dubbed "swine flu" and also known as influenza A/H1N1, emerged in Mexico, the United States, and several other nations.
Split into simpler sentences: In April 2009 a novel flu strain evolved that combined genes from human, pig, and bird flu. Initially dubbed "swine flu" and also known as influenza A/H1N1, it emerged in Mexico, the United States, and several other nations.