Hadith 2829
Narrated Abu Huraira: Allah's Apostle said, "Five are regarded as martyrs: They are those who die because of plague, Abdominal disease, drowning or a falling building etc., and the martyrs in Allah's Cause."
Hadith 2830
Narrated Anas bin Malik: The Prophet said, "Plague is the cause of martyrdom of every Muslim (who dies because of it).