I grew up in deep East Texas. Those of you who have never visited Texas might be thinking
of tumbleweeds, cacti, and rednecks. You'd be right on one of those three. North east
Texas at least in parts, is a swamp. The part just adjacent to Louisiana is everything you
expect of a semi-tropical swamp. Hot, humid, and lots of little black water lakes. I used
to love to swim, dive, and fish in the local lakes.
I tell you this to give you background on why I will never... not ever... absolutely
never, ever, ever go back into a warm, freshwater lake ever again. It used to be one of my favorite
activities, but one thing ruined it. PAM.
Pam is not an ex-girlfriend or creepy old nudist lady. It's not a person at all. It's
primary amebic meningoencephalitis. P - A - M. It's a very, very rare health threat,
only 32 proven cases in the last decade, about a hundred in the history of the US. 28 of
those cases were from swimming in freshwater ponds, lakes or pools, 2 were from a drinking
water supply that was heated geothermally, and two of those infections were the result
of watching Oprah.
Okay, not watching Oprah *exactly*, but those two cases were the result of using neti pots,
and the neti pot craze certainly started on Oprah's talk show.
I'm going to talk about PAM, and I'm going to talk about neti pots. Then I'm going to
summarize what the real risk connection is between those two things.
1. A little more about PAM: It's horrible. We have no tests to diagnose
it. We have no drugs that we know work on it. If you contract PAM, you have only a 2%
chance of surviving. It's a death sentence, and it will be a painful, lingering death.
I have studied Ebola and Lassa, I have been in Biosafety Level 4 facilities and this thing
scares me irrationally.
The causative agent in PAM, typically an ameba called "Naegleria fowleri", needs warm fresh
water to thrive and grow. That's why cold water lakes are relatively safe. It's also
no threat for drinking water, as stomach acids destroy it quickly. It's only route to penetrate
your defenses is in the nose. Since prior to humans swimming in warm freshwater for
recreation, and of course since Oprah suggested pouring warm water into your nose, the disease
has increased in prevalence.
Hey, bonus depression: Thanks to a warming trend, lakes as far north as Ohio are likely
to be infectious during the summer months, signaling a general trend of expansion. If
you wonder where this stuff was when you were a kid, jumping off a tire swing into the local
watering hole, the answer is that it was much further south in the tropics.
The amebic agent goes through multiple stages in its life cycle, including a cyst stage
where it can remain dormant and protected from its environment for years. Yes, that's
right, it can survive cold, starvation, toxic chemicals and desication and still pop up
and eat your brain.
2. Are neti pots effective? Actually, yes, a little. Running warm isotonic
salt water does help to moisturize and wash out the crud from the little hairs in your
nasal sinus. It's not rocket science. The warmth, moisture and flushing effect can be
pretty soothing. That's why it's been used medically for decades following sinus surgery
to wash out wounds. The neti pot is a bit of silliness, invoking the ancient wisdom
fallacy that anything that's been practiced for thousands of years must be effective.
Anyone who thinks that doesn't know humans very well.
There have been multiple papers studying the effectiveness of nasal irrigation, whether
the irrigation is done with a plastic squirt bottle or vitrified ceramic neti pot, it does
reduce swelling and pressure. A Cochrane Database review (of all available literature) found
that "There is evidence that saline is beneficial in the treatment of the symptoms of chronic
rhinosinusitis when used as the sole modality of treatment. Evidence also exists in favour
of saline as a treatment adjunct. No superiority was seen when saline was compared against
a reflexology 'placebo'. Saline is not as effective as an intranasal steroid." There
are also Cochrane reviews of saline nasal irrigation for acute upper respiratory tract
infections, but the results there are not encouraging.
The side effects are nasal soreness, and can include nosebleed and headache. If you want
to avoid the side effect of death by brain-eating ameba, you should never, never use tap water.
You should boil then cool or otherwise sterilize any water that goes in your nose. The neti
pot or other container should be thoroughly cleaned after each use and allowed to air
dry.
In short, properly used, the neti pot is about as effective as any other folk remedy at making
you feel better, but it doesn't address the root cause of nasal troubles. It's not as
effective as a steroid, but the side effects are pretty mild.
3. Now, to summarize the real risk of PAM from nasal irrigation.
The absolute risk is fairly easy to calculate as long as we can make up some numbers. 2
reported cases, assuming that's pretty good coverage. I have no reliable numbers on how
many people use neti pots, but let's use a plausible number of 1 million in the US. Given
our wild guesses, the incidence of PAM is 2 cases in 1 million exposed, or 0.2 cases
per 100,000 in 10 years. The per year number moves one more decimal, 0.02 cases per 100,000.
The incidence of lightning strike is about 0.1 cases per 100,000 in the general US population
of about 300 million. That means that the risk of PAM is about equivalent to the risk
of any given person getting hit by lightning.
Oh, that's not proper epidemiology, but the absolute risk is pretty small.
Of course, if the water is pre-filtered, boiled and cooled; the pot cleaned and air dried
after every use, the risk is essentially zero, or at least has never been measured to be
more than zero. Every case so far has been the result of using tap water.
So, my final verdict on neti pots? Well, even a stopped clock is right twice a day. Oprah
gets a pass on this one. Neti pots are relatively safe, so long as you take some very basic
precautions and never, never, never use tap water in them. If PAM scares you as much as
it scares me, you can be excused from a little irrationality, but if you are looking for
a realistic assesment of risk, you are thousands of times more likely to die from slipping
in the shower or falling off a ladder.
Why am I so against swimming in warm water lakes of my native Texas? We established that
the absolute risk is really quite low. Even though the risks are higher for getting PAM
from swimming, the relative risk ratio, that is a comparison of the exposed and unexposed
populations, would be relatively high. The difference in disease rates among non-lake
swimmers and non neti-pot users is relatively large. Sitting here at my computer, there
is almost no chance that a brain-eating ameba will be lurking in the shadows, preparing
to pounce upon and devour my delicious head meats.
The moment I dip a nostril in Caddo Lake, however, PAM is just waiting for me. Possibly,
maybe, probably not... but I'll be darned if she's going to get my cerebrum.
Thanks for watching.