Hot pool Horrors.

Whilst on holiday at Hanmer Springs I couldn’t help but notice the signage.

“Keep head above water!” “No diving or splashing!”

With a 3yo whos idea of not splashing involves a small tsunami each time he hits the water I wondered about the risk and history of these signs.

So what is everyone so worried about?

PAM (Primary amoebic meningitis.)

Caused by Naegleria fowleri a nasty little amoeba which lives in warm soil and can survive for long periods in inadequately chlorinated or filtered warm water. After being “forced” into peoples nasal passages it migrates to their brain and causes an almost always fatal meningitis. (1)

(Hanmer looking lovely below)

The first recorded New Zealand outbreak of amoebic meningitis was in 1968-1978 (8 cases) which lead to the implementation of standards to reduce the risk of infection. (2)

Now pools are classified as naturally occurring pools which are considered high risk and lower risk commercial pools which are required to meet a standard. These pools which usually have a constant flow of water, are filtered and chlorinated. Other important techniques to reduce the incidence of N. Fowleri in the water are foot washes and having no bare soil near the pools themselves. (3)

New Zealand has a large number of geothermal areas and many of these are considered high risk as they are pools which may be dug from the side of a river bank or in some cases out of the earth. (Eg: Welcome Flat hot pools below)


In recent times in 2010 there was another 2 cases in the central north island. (2) Which again lead to improvements in a number of bathing areas.

Quantifying risk is very difficult but some epidemiologists have had a go!

“French epidemiologists estimate that given 10 N. fowleri amoebae per litre of water and a likely inhalation or ingestion of 10 ml of water during swimming, the risk of human infection for a swimmer is 8.5 x 10-8!5” (2)

So clearly pretty low risk but as the diagnosis is often elusive. Eg: unwell male in his 50s with no fever just feeling terrible and no meningeal signs. (4) This often which leads to late treatment which is not very effective with only occasional case reports of survivors (5)

Treatment is usually with IV +/- intrathecal amphotericin  but most patients have had multiple other drugs including standard meningitis therapy (here: ceftriaxone) by the time a diagnosis of PAM is suggested. (2)

Thanks to good public health measures PAM has been reduced to only occasional case reports. It seems that an ounce of prevention really is worth a pound of cure.

Might try keep the lad from dive bombing the sulfur pools next time we are there.



1)The epidemiology of primary amoebic meningoencephalitis in the USA, 1962-2008.       Yoder et al.

2) A case of primary amoebic meningoencephalitis North Island New Zealand.

3) NZ Ministry of health PDF:

4) N Z Med J. 2004 Feb 20;117(1189):U783; author reply U783.
Primary amoebic meningoencephalitis presenting without fever.
Bond B. (GP discussion)

5)A rare case of survival from primary amebic meningoencephalitis Gautam et al

Speak Your Mind