Messenger of Allah ﷺ 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."  

أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ الشُّهَدَاءُ خَمْسَةٌ الْمَطْعُونُ وَالْمَبْطُونُ وَالْغَرِقُ وَصَاحِبُ الْهَدْمِ وَالشَّهِيدُ فِي سَبِيلِ اللَّهِ  

The Prophet ﷺ said, "Plague is the cause of martyrdom of every Muslim (who dies because of it).  

عَنِ النَّبِيِّ ﷺ قَالَ الطَّاعُونُ شَهَادَةٌ لِكُلِّ مُسْلِمٍ