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The 1st Wave
Ten days after the "mothership" was spotted passing mars, a massive elecromagnetic pulse wiped out everything from cell phones to vehicles including airplanes and cars. This killed about half a million people. -
The 2nd Wave
Within one day of the 1st wave the 'Others' from the mothership wiped out everything within costal regions, killing over 3 billion people. -
The 3rd Wave
This wave took longer to develop. Birds, having no limit, carried a deadly virus all over the earth, spreading it rapidly. This took out more than 3.5 billion people. -
The 4th Wave
The book takes place in this wave. The "Others" supposedly look like people, so you can't trust anyone who is a person.