I love Brazil and my Brazillian sisters but a friend of mine was there for a week and some days this month and she was robbed 3 times and a guy randomly punched her in the back out of nowhere, this was in Rio, I was sure I wanted to visit Brazil before this
Unless you go to the Amazon, there is no need to worry
From what I've heard there are quite a few venomous spiders and scorpions in the cities, though if I'd go to Brazil I would want to go to the Amazon, it's one of the most beautiful places in the world