NEW YORK (Bloomberg) ? Insurance claims could increase as much as $47 billion in the event of a bird-flu pandemic killing 609,000 people in the US and Europe, Fitch Ratings said.

If a pandemic killed 400,000 people in Europe, insurance claims would increase by ?20 billion ($29 billion), the ratings company said today in a news release. A pandemic killing 209,000 in the US could increase claims by $18 billion, said Fitch, which based its estimates on "published expert opinions".

As well as mortality claims, life and other insurers would suffer market declines if there's a flu outbreak in humans, Fitch said. It does not envisage a "significant threat" of widespread ratings downgrades at present.

"Downgrades would be most likely if the virus mutates to allow human-to-human transmission and leads to a considerable increase in mortality claims or investment-market losses," said Lauren Kalinowski, an associate director at Fitch's US insurance group in New York in the release. "The companies most affected would be those with concentrations of mortality risk."

Experts disagree on the number of people who may die from bird flu.