Sadly, today I found out that a friend of my family has just passed away. The cause of her sudden death was a brain aneurysm. I have been researching brain aneurysms and have found out that oral contraceptives are thought to sometimes cause them. I am 19 and I am taking birth control, and now I am very worried. Can you give me some statistics about brain aneurysms linked to oral contraceptives? Thank you.

I have heard numerous reports in the media where they make mention of the "live flu virus" in the flu vaccine, specifically "flu-mist." This is mentioned in conjunction with a warning to avoid contact with this and that (yadda, yadda) for a certain time period. This confuses me. I was under the impression that the flu vaccines contain dead viruses and that it was not possible to catch the flu from the vaccine. Which is it?

I'm wondering about Lyme disease and chronic fatigue syndrome — the differences and similarities?

If you step on a nail and have not had a tetanus shot in the last five years, how soon should a person be vaccinated? 24 hours? 48 hours?

I use Nalgene bottles for about 75 percent of the water I drink each day. Therefore, I was startled to find out that there is some possibility that these bottles leach chemicals into the water. I've found conflicting opinions about the veracity of these claims on the Internet. What's the truth? Should I dump my Nalgene for glass? You have an earlier post about bottled water, but it doesn't seem to address this issue specifically, and you recommend purchasing reusable bottles like the ones that might be poisoning me. The bottles I use have #7 on the bottom in the recycle symbol.

1) This is in reference to your Missed periods Q&A. Another cause of missed or late periods is PCOS (polycystic ovary syndrome). A lot of health care providers don't seem to be aware of this syndrome. In this syndrome, missed or irregular periods are caused by unusual hormone levels, sometimes in combination with insulin intolerance. Because missed and irregular periods cause scar tissue build-up in the uterus (which may cause endometrial cancer) and may cause infertility, it is important that your readers know to ask their health care provider about this syndrome. There are obviously other symptoms and complications, but I just thought that I might mention it to you so that you might read up on it for your readers. Thank you.

2) I was recently diagnosed with polycystic ovary syndrome (PCOS). I'm only 17 and am afraid that this will affect my chance of having children. Should I worry? Also, I know birth control pills will help me regulate my period, but if I take them, will it stop the effects PCOS has on me? Like me gaining rapid weight, missed periods, and losing my hair? This is really worrying me. Can you inform me on this syndrome?