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.
It is based on a June meeting of experts charged with making recommendations on how to reduce health risks during the hajj. Scientists from the UN Centres for Disease Control and Prevention (CDC) and the World Health Organisation (WHO) also contributed to the findings.
The Lancet questioned, though, whether these measures would be widely accepted or effective.
"Because hajj is one of the five pillars of Islam and should be done at least once in a Muslim's lifetime, individuals will probably not want to postpone after they have spent much time saving money and planning for this purpose," it said in an editorial.
A policy of isolating sick pilgrims might backfire by discouraging those with flu-like symptoms from reporting their illness, it added.
Saudi authorities have separately called on hajj pilgrims to get vaccinations for seasonal flu and, where possible, for the A(H1N1) pandemic flu as well.
Out of more than half a million pilgrims who had arrived as of last week, nine were diagnosed with swine flu, the Saudi health ministry said on Wednesday.