Mountain sickness

What is it ?

Mountain sickness (also known as “altitude sickness”) is experienced by some travellers after climbing or hiking for over 6 hours in mountains at high altitudes. The air is thinner at high altitudes and the oxygen supply is correspondingly lower, making it more difficult to breathe. The symptoms resemble a hangover caused by alcohol. They occur after 10 to 14 hours spent at altitudes over 2,500 metres (8,125 feet) above sea level.

Disease transmission

Geographic risk zone

Mountain sickness can occur in any mountainous region where the altitude is higher than 2,500 metres.

Symptoms description

Acute mountain sickness

Nausea
Loss of appetite
Dizziness
Headache
Insomnia
Lassitude (general fatigue)
Shortness of breath

Ignoring the initial symptoms can lead to serious complications, including neurological deterioration (cerebral edema) or respiratory failure (pulmonary edema).

Cerebral edema

Problems coordinating body movements while walking
Unusual behaviour
Loss of consciousness (starting with intense headache and leading to coma and eventual death)

Pulmonary edema

Dry, throaty cough
Coloured secretions (pinkish to red blood)
Respiratory distress (developing rapidly and possibly resulting in death)

Health impact

Although mountain sickness is a state of physical distress rather than a disease caused by microbes, its consequences are no less serious. If the initial symptoms are ignored, the resulting complications may require emergency medical treatment. Without prompt intervention, mountain sickness can even be fatal.

Risks

According to the Public Health Agency of Canada, being in good physical shape does not protect people from acute mountain sickness if they ascend to high altitudes too fast, or spend more than half a day at altitudes higher than 2,500 metres.
The PHAC also points out that the correlation between this illness and altitude is very real. In the Swiss Alps, mountain sickness has been observed in 9% of mountain climbers at 2,850 metres, 34% at 3,650 metres and 53% at 4,559 metres.

Prevention

There is no vaccine to protect you against mountain sickness. If you become ill, descending to a lower altitude remains your best remedy.

One preventive drug is available with a prescription: Diamox, which experts recommend for travellers who expect to make a rapid ascent (in 24 hours or less) to heights 3,000 metres or more above sea level. This treatment is also recommended for those who have reacted badly to high altitudes in the past. However, Diamox is contraindicated if you have known allergies to sulfa drugs such as Septra or Bactrim.

When ascending to a high altitude, drinking water frequently in small amounts (about 3 or 4 litres per day) will help your body adapt. You’ll know that your water intake is sufficient if your urine is practically colourless.

Whenever possible, spend the night at an altitude that’s lower than the highest point you reached during the day, but higher than the day before. Once you’ve reached 3,000 metres or higher, don’t sleep at a height that’s more than 600 metres above the altitude you reached the day before. For every 600 to 900 additional metres, make sure to sleep two nights in the same place.

As soon as you feel the first symptoms of mountain sickness, stop your climb immediately. Take time to rest, and then descend. Symptoms take 3 to 7 days to disappear.

Depending on your medical history, other drugs may be prescribed by an expert travel health physician.

The Public Health Agency of Canada strongly recommends that all travellers consult a travel health specialist before they go abroad. Your specialist will be able to advise you about various resources and options available so that you can protect yourself effectively against this illness.

Vaccination : mountain sickness

Recommended products

None

Nota Bene

There’s no relationship between an individual’s physical shape and a possible predisposition to mountain sickness. In many cases, deaths at high mountain altitudes are actually the result of an unduly rapid climb of the sort that being in top physical condition makes possible.
Pulmonary edema, a complication of mountain sickness, generally occurs during the second night spent at a high altitude.
Consumption of alcohol or sedatives increases the risk of complications due to mountain sickness.