People at risk of suffering severe consequences from swine flu should postpone going to the hajj in 2009, according to a study released on Saturday.
Some 2.5 million Muslims from more than 160 countries converge annually on the Islamic holy cities of Mecca and Medina in western Saudi Arabia.
The hajj pilgrimage, to be completed at least once in a Muslim's lifetime, under the tenets of Islam, can be undertaken at any time, but peaks this year from November 25 to 29, at the height of the alert over swine flu.
The study recommends that pregnant women, the elderly, individuals with chronic diseases and children who intend to participate in the 2009 hajj do so at a later date.
Secondary recommendations include providing persons showing flu-like symptoms with hygiene packs and information brochures, and setting up isolation facilities for those infected.
On average, each person infected with the 2009 pandemic flu spreads the virus to another 1.4 individuals.
But during the climax of the pilgrimage, when crowds can reach a density of up to seven people per square metre (10 square feet), the risk of infection could be much higher, the report said.
"These preparedness plans should ensure the optimum provision of health services for pilgrims to Saudi Arabia, and minimum disease transmission on their return home," the researchers said.
The study, published in the British medical journal The Lancet, was led by Ziad Memish of the Saudi Arabian health ministry.