How many letters does the top answer for “likely to spread and cause an epidemic disease” have?

The most common answer is pestilent (9 letters).

Crossword clue: likely to spread and cause an epidemic disease

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

pestilent 9 letters wn-def

likely to spread and cause an epidemic disease

pestilential 12 letters wn-def

likely to spread and cause an epidemic disease