So you haven't actually been tested for it and have no symptoms? Is the water somewhat warm? A LOT of people get exposed to fresh water by rafting or swimming and so forth and they don't get this amoeba or anything else, but I'll give you the facts and you can decide for yourself:
The good news is that it is very rare to get the infection. According to the CDC only 33 people got infected with Naegleria fowleri between 1998-2007 and that if treated right away has a good chance of survival, but the bad news is if you get it it is fatal unless treated right away. If treated you have a good chance of survival if you actually have the organism. Note that you don't know you have it and it is rare. So, the symptoms can arise anywhere within 24 hours to 7 days but the other amoeba may be different. The symptoms are and can be variable: headache, stiff neck, high fever, double vision, vomiting, nausea,and coma so forth. I would see a doctor that would test for this. Probably an infectious disease specialist would be best. Explain to them that you were in contact with fresh water and are afraid of exposure to N. fowleri. They can test nasal, eye samples etc. They can test your spinal fluid and if they do and you have the organism the white blood cells and red blood cells would be very high and the glucose I believe is low. The treatment is with Intravenious and Intrathecal (injection into the spinal fluid) of antibiotics Amphotericin B, Micronazole, and oral Rifampin. Alternatively, they can try Azithromycin and voriconazole. Most likely you are negative and if you get symptoms you have to go in for treatment immediately. There are other amoeba called Acanthamoeba and balamutha , Sappinia, diploidia and so forth that aren't as fatal but can cause eye damage and are problematic too but are also rare. It still doesn't mean you have it. So, I would have a talk with a doctor that is knowledgeable in the area as soon as possible to have them decide whether you should start testing or wait to see if you get symptoms. Again it is a rare bug but since it is so fatal without treatment you may want to err on the side of extra caution.
I hope this helps and doesn't make you worry more.
hi again, Since you are so worried I wanted to say again of all the swimmers, rafters and people in all the U.S. that were in warm waters only about 7 per year or 33 in the years between 1998-2007 (10 years) did anyone get N. fowleri. It is so rare that they don't routinely look for it in the lab unless the person has symptoms and has been in fresh warm water. So, try not to worry. I understand your concerns I just wanted to inform you of what to look for just in case you find symptoms or decide you want to see a doctor. Let me know how you are doing.
do charcoal crystals in a stool test definitely mean that you have an amoeba?