MO Missouri Porch

Rivers, Tubing & Water Safety

Water quality & getting sick

A river is natural water, not a pool — and a few healthy-swimming habits keep you fine the vast majority of the time. Here's what the advisories mean, what to watch for, and the calm, simple steps that keep you well.

E. coli and swim advisories

E. coli is normal in natural water — a river isn't a swimming pool. Higher-than-natural levels (often after heavy rain washes in runoff and animal waste) can pose a risk. The DNR samples designated state-park swim beaches weekly from Memorial Day to Labor Day — not every swimming hole. By law, a geometric mean above 190 E. coli per 100 mL triggers a 'swimming not recommended' posting (RSMo 640.080). Swallowing water over that level is mainly tied to stomach illness — and sometimes ear, eye, or skin infections — which is why a posting means swimming isn't recommended. A result is a snapshot for one spot at one time, and a clean-looking gravel bar is not a tested beach.

Harmful algal blooms (the paint-scum)

Harmful algal blooms (blue-green algae, or cyanobacteria) grow in warm, slow, or pooled water — mostly lakes and ponds, less often on fast rivers. They can look like spilled paint, scum, or thick foam, and they can make you sick through skin contact, swallowing, or breathing in spray. When in doubt, stay out. Keep children and especially dogs away, and follow DNR and DHSS advisories.

Naegleria (the rare one)

Naegleria fowleri (the 'brain-eating amoeba') is very rare but very serious. It lives in warm freshwater and infects through the nose — not by swallowing. The simple, low-stress precautions: keep water out of your nose (hold your nose or use nose clips when you jump or dive in), avoid warm, stagnant freshwater in the hottest weather, and don't stir up warm, shallow sediment. It's rare — don't let it keep you out of the water; just take the easy precautions. One thing worth knowing: if someone gets a sudden severe headache, fever, and stiff neck within a couple of weeks of swimming in warm freshwater, treat it as an emergency — go to the ER now and tell them about the water.

Leptospirosis

Leptospirosis is a bacterial illness spread through animal urine in water, entering through cuts, eyes, nose, or mouth. Cover your cuts, don't swallow river water, and know the risk is higher after flooding.

Swimmer's itch

Swimmer's itch is an itchy rash from a parasite that can't survive in people. It usually clears on its own but can last a week or more. Towel off and rinse right after you swim, try not to scratch (broken skin can get infected), and see a doctor if the rash is severe, spreading, or won't go away.

The simple habits

Six things that keep you well

  • Don't drink the river.
  • Keep your head out of warm, stagnant water.
  • Cover any cuts before you get in.
  • Rinse off after you swim.
  • Don't swim if you have diarrhea.
  • Skip water that looks or smells off.

If someone gets sick after the water

If someone gets sick after being in the water — a high fever, a severe headache, or stomach illness — see a doctor and mention the water. Report harmful algal blooms or possible illness to Poison Help or the DHSS hotline. In an emergency, call 911.

Poison Help: 800-222-1222  ·  DHSS: 800-392-0272  ·  Emergency: 911

Before you float

Missouri Porch explains; the people who run the river decide.

Last checked: 2026-06-18. Rivers change by the day — the level, the weather, and the water-quality advisories are different every time. Check the live gauge and the forecast before every float, and wear your life jacket.

This is a plain-English summary — not the law, a medical authority, or a substitute for a guide or a swiftwater course. River levels, rules, and advisories change — check the live gauge, the forecast, and the agency or outfitter before you float. In an emergency, call 911.

Heads up: This is general information, not medical advice. A clean-looking gravel bar is not a tested swim beach — and if someone gets sick after the water, see a doctor and mention it.

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