Dr. Mahmoud al-Srouji peers at a laptop computer screen showing technicolor images of a group of Indian pilgrims filing by, just off a flight from Mumbai in Jeddah airport's massive hajj terminal. "They don't know that we are already checking them," he said, referring to the small thermal camera scanning each person for a high body temperature.
"It rings if the temperature is over 38 degrees (Celsius, 98.4 degrees Fahrenheit)," he said. "It is so sensitive, if you light up a cigarette way over there, it will sound," he said.
It is Saudi Arabia's first line of defence for the annual hajj, with fears over the swine flu pandemic, which has already killed four pilgrims, dominating the preparations to receive some 2.5 million Muslims in the holy cities of Mecca and Medina.
Srouji is just one cog in a massive operation to make the hajj work - several hundred thousand security officials, health workers, guides, translators, religious advisors and baggage handlers vying to do the impossible and make sure few get sick, lost, robbed or left behind on their once-in-a-lifetime trip to the holy land where Islam began.
At Jeddah airport, Javeed Ahmed of Mumbai is on his 14th trip leading dozens of Indians on the hajj.
He said the Saudi management has improved year by year, and newly rebuilt hajj terminal arrival facilities have vastly alleviated past hassles.
"This is much better than before," when tens of thousands of people would be pushing and shoving in passport and luggage queues.
It is chaos, but altogether pretty efficient, says French consul Christian Nakhle, who has to care for as many as 30,000 pilgrims coming from France.
"We all work 24 hours a day, seven days a week for several weeks," he said.
Jeddah is the main port of entry for pilgrims heading to the nearby holy places.
At the airport's hajj terminal - an airy structure looking from a distance like a desert Bedouin encampment - a passenger jet lands every few minutes, disembarking pilgrims from around the world into a huge hall decorated with welcome banners and Panasonic advertisements.
It is a huge mixing bowl of ethnicities and germs. But Srouji said that of the 5,000 people a day who pass by his camera alone - there are 11 other such stations - so far he has picked up only one person with a feverish temperature.
As well as the flu, the doctors police for vaccinations, and have already pushed on arriving pilgrims 300,000 oral polio vaccines, and 100,000 meningitis prophylactic-antibiotic combinations.
"We have to watch them take it," says the terminal's medical director Dr. Mohammed al-Harathy.
Caring for so many is not just a government effort. Hundreds of travel agents and foreign missions are all working round the clock to deal with myriad problems, says Nakhle.
The French consulate has brought in extra staff to deal with the inevitable medical emergencies and lost passports and other travel problems.
Last year, for instance, an aircraft showed up two days late to pick up its load of returning, hotel-less pilgrims.
This year, he has three French-speaking doctors on call full-time, three dedicated motorcycle drivers to get documents and other supplies through impenetrable Mecca traffic, and roll-up mattresses for staff inside Mecca who follow the French hajj groups around full time, but sometimes cannot get back to their hotels.
The motorcycles are crucial, he said. A year ago, a French pilgrim appeared to be having a heart attack. They had to load the man on the back of a motorcycle to get him through the traffic to where a car could take him to hospital.
Eventually, the consulate had to organise a flight for the man and a doctor to accompany him back to France for treatment.
In addition to sleepless days and nights, taking care of the French pilgrims "involves a lot of money," Nakhle said.