Hospital managers are asking police for intelligence on whether Doomsday sects plan to travel to the Meridian Line, centre of world time, on New Year's Eve.
The information is being written into emergency plans being developed by Bexley and Greenwich Health Authority, which runs the three emergency hospitals in south-east London. Its managers are also having to consider the possibility of terrorist outrages to interrupt the celebrations, when at least 500,000 people are likely to be drawn to the Millennium Dome and Greenwich Park, through which the Meridian runs.
Other possible disaster scenarios include the possible collision on the Thames of some of the boats expected to pack the river, filled with sightseers viewing several firework displays.
Health authority chief executive Michael Kerrin told the Independent on Sunday: "We haven't seen anything like this in Greenwich. Because of its unique nature, there's a limited amount of local experience. One big difference about this event is its scale."
Concerns that the turn of the millennium might induce a suicidal hysteria akin to that which swept medieval Europe at the start of the year 1000 have exercised minds.
"Jerusalem is preparing for various sects turning up, thinking that it's going to be the end of the world," said Mr Kerrin. "We're not expecting something similar, but people who might have gone elsewhere might come in our direction. The police will have to assess the risk of various kinds of millennium fever. We will tweak our general plan as a result of that intelligence."
Another problem could be having to deal with unstable revellers, who might be seized with a mental illness because of the size and emotional state of the crowds.
"Isolated individuals could panic, because they are exuberant or because there are so many people around them," said Mr Kerrin. "They would be either a risk to themselves or hysterical. Whether they are falling around or whether they have some sort of offensive weapon, we deal with the consequences.
"More mundane casualties are almost guaranteed, including crushing in the crowds, drunkenness and fights, although significant disorder is not expected. We're planning for people to have a good time. This ought to be a happy crowd, but it will be exuberant by the end of the evening."
The authority is trying to ensure that its hospitals are adequately staffed for the night. Managers might offer significant pay increases for the millennium weekend, as well as time off in lieu.
Some staff contracts enable managers to order compulsory work, but Mr Kerrin said he hoped these would not be used. If there was a disaster, he believes off-duty staff will flock to work. Staff at Greenwich hospital have already been told they cannot book leave during the celebrations.
A London-wide advisory group has been set up to explore the problem. Mr Kerrin said it was looking at inflated pay for the night, when bar workers could command hundreds of pounds for the shift.
"We expect the millennium weekend will be busy for the health service," he added. "We're likely to have more people on duty than fewer, but precisely how many, we don't know."
One problem will be deciding which hospitals will take the strain. With huge crowds blocking access points, ambulances will have a difficult task ferrying casualties. Some bridges over the Thames could be closed to traffic, barring access to north London hospitals.
No extra Government money has been allocated to deal with the millennium. But the New Millennium Experience Company is funding a minor injuries unit, with a doctor, two nurses and a paramedic, to look after VIPs on the night and the thousands of daily visitors for the rest of the year.