Complex sentence: Before antivenom was introduced, it is reported that about 50% of death adder bites were fatal although deaths are much more rare nowadays as the anti-venom is widely available and the progression of envenomation symptoms is slow.
Split into simpler sentences: Before antivenom was introduced, it is reported that about 50% of death adder bites were fatal. Deaths are much rarer nowadays as the anti-venom is widely available and the progression of envenomation symptoms is slow.