How did tom sawyer parents die from what illness?

Tom's father and mother were simply dead. No details to their deaths is given or as to why he came to live with Aunt Polly and cousin Mary with his half brotherr Sid ( a year or so younger) . No mention is made of the relation of Sid to Tom (whether Tom and Sid as half brothers share mother or a father) . Tom is the son of Polly's dead sister.