How bad is swine flu? Without numbers, who knows?

By Maggie Fox, Health and Science Editor

WASHINGTON (Reuters) - Many people are confused about just how many patients have been infected with the new H1N1 flu, which in turn makes it hard to tell how bad the pandemic is, British researchers said on Tuesday.

But better methods of measuring the swine flu toll in real-time could help reduce some of that confusion, according to the team at Imperial College London.

And without this information, they said, governments are operating in the dark when assessing what their response should be.

"If you don't test people, you don't know how many people are out there who have it," Dr. Tini Garske, an expert in disease modeling who led the study, said in a telephone interview. "The number of confirmed cases doesn't tell you a lot."

The World Health Organization has confirmed 94,512 cases globally and 429 deaths from the new H1N1 swine flu, which was declared a pandemic last month.

But these numbers represent only a fraction of the real cases -- the U.S. Centers for Disease Control and Prevention says at least a million people have been infected and the virus is spreading out of control.

Most countries are now only testing a sample of patients, and many people who become infected are not ill enough to even seek medical attention, let alone get tested.

Diagnostic kits for H1N1 are expensive, and most governments save them for when they are really needed.