The illness is believed to be caused by a defective gene.据信，这种疾病是由基因缺陷引起的。The recent floods are said to be caused by climate change in the northern hemisphere.最近发生的水灾据说是由于北半球气候变化造成的。Her chest pains turned out to be caused by a minor heart attack.她胸口疼痛是由轻微心脏病发作引起的。