BETHESDA, Md. (AP) _ The planet may be overdue for a new worldwide epidemic of influenza, one of humanity's oldest and deadliest disease enemies, international experts said at a conference here Wednesday.

More than 200 infectious disease experts met this week to consider how they should prepare for what some believe is the inevitable rise of a new and lethal influenza virus.

``A new pandemic is possible,'' said Dr. Dominick Iacuzio of the National Institute of Allergy and Infectious Diseases. ``We can't lose sight of the fact that influenza agents have the potential to cause a lot of morbidity and mortality. It has happened before and it can happen again.''

The last major worldwide flu epidemic was in 1968, the so-called ``Hong Kong flu,'' and new strains of the flu virus typically rise and sweep through the international population every 10 to 40 years.

From the perspective of history, said Iacuzio, ``some experts say we are overdue.''

The influenza virus regularly and rapidly rearranges its gene structure. Every now and then, a viral strain develops that humans have never before been exposed to, which can be the start of a pandemic, said Iacuzio.

Between 1918 and 1919, a new viral strain infected more than 2 billion people and killed an estimated 20 million to 40 million, more than a half million in the United States.

The ``Asian flu'' in 1957 also was new. It quickly circled the globe, causing widespread social disruption and at least 750,000 deaths in the United States.

Iacuzio said the Bethesda conference, organized by the NIAID, was called to help sort out how experts worldwide can prepare for a pandemic and identify gaps in what is known about the flu virus and its control.

A formal report is still being prepared, but these findings will be among the conclusions, he said:

_ Increased surveillance efforts, particularly in remote Asian areas, are needed for early detection of new flu viral strains. There currently is a network of 110 labs in 80 countries. If a potentially deadly new form of the flu is found early enough, said Iacuzio, the pandemic could be blunted by rapidly producing a new vaccine. Surveillance could include collecting specimens from early cases and sending them to central laboratories for analysis.

_ More research is needed to understand the response of the human body to the virus. Conclusions based on animal studies may not apply to humans and researchers need to validate such research to develop more effective drugs.

_ Some experts believe the concentration of proteins used in the flu vaccine may be reduced, thus making more vaccine doses available. ``We don't know the answers to this,'' said Iacuzio, and that knowledge could be critical if there is a sudden, worldwide need for vaccine.

_ Final work on vaccines that can be applied as nose spray or nose drops must be completed. These so-called ``cold adapted vaccines'' use modified live virus and have been shown to be effective in some studies. Iacuzio said their availability in a pandemic could save many lives by protecting people against the disease.

_ Antivirals, drugs used to treat the flu infections, could provide physicians with important new weapons in treatment of patients already infected. Iacuzio said there are candidate drugs being tested, but not now available. Such drugs need to be speedily developed, he said.