Each year, 10 percent of the world's Muslims, or two million people, travel to Mecca to participate in the Hajj, a journey that is considered compulsory to Muslims who are able to physically travel and afford the trip. This year, the five-day pilgrimage will take place in early January. But, British doctors are warning that there may be significant health risks to pilgrims that can include sunstroke, heat exhaustion and infectious diseases.

In a report published in the British Medical Journal today, doctors have listed some of these risks and means by which to avoid suffering ill effects. To avoid too much exposure to the sun, pilgrims should travel by night and carry an umbrella. Additionally, they should drink lots of water and wear sturdy shoes.

The article warns, 'In view of the very large numbers of people from disparate regions and the hostile climate of the Arabian desert, the chances of disease, particularly in elderly and infirm people, are high.'

As pilgrims travel through the desert in high temperatures, the risks of heatstroke and exhaustion are elevated. People are expected to camp in the desert and walk long distances. Thus, travelling by night is recommended.

Doctors are concerned that men, who are forbidden from covering their heads during this journey, will forgo carrying umbrellas, putting themselves at higher risk.

Pilgrims are required to be vaccinated against meningococcal meningitis before entering Saudi Arabia. They should also be vaccinated against Hepatitis A and B and take anti-malarial tablets.