Chicago ? Amid worries about bird flu, demand for a flu medicine is so extreme that the drug’s maker has stopped shipping it to private U.S. suppliers just as consumers fret over whether they should try to stock up on the drug.

Tamiflu, a prescription drug designed to treat regular flu, is running scarce because of worries the bird flu in Asia might morph into a contagious human flu that circles the globe.

Tamiflu’s maker, Roche Holding AG in Switzerland, said Thursday it was temporarily suspending U.S. shipment because of increased global demand. Company officials have previously said they are limiting supplies to pharmacies to thwart hoarding.

But there are signs that is happening.

“We’ve seen recently some very large purchases at the wholesale level, companies or large entities who are possibly hoarding Tamiflu right now,” said Darien Wilson, spokeswoman at Roche’s U.S. offices in Nutley, N.J.

Prescriptions for the drug last week were nearly quadruple what they were a year before, according to Verispan, a Pennsylvania-based company that monitors pharmacy sales. Some health departments and doctors’ groups are urging consumers, doctors and even school districts not to stockpile the drug.

And this winter’s flu season hasn’t even started yet.

“The priority is that there is enough Tamiflu for the people who need it at the start of the influenza season,” said Roche spokesman Alexander Klauser. “At the moment, there is no influenza currently circulating.”

Meanwhile, the U.S. government isn’t giving advice on whether people should have a stash of Tamiflu, just in case bird flu triggers a human pandemic.

“Those are questions that are under discussion,” said Christina Pearson, spokeswoman for the U.S. Department of Health and Human Services. “Right now we’re focused on the seasonal flu.”

HHS includes the federal Centers for Disease Control and Prevention, whose job includes public health recommendations. The agency’s silence on the issue of hoarding has frustrated some local health departments.

“A lot of people have asked the CDC to provide some guidance about this, with patients asking doctors for prescriptions,” said Dr. Craig Conover, medical director for the Illinois Department of Public Health.

Personal hoarding isn’t fair, he said, “but on the other hand, I have heard people say that the more this gets used, the more manufacturing ability they’ll develop. We’ve chosen to wait for CDC guidance on this.”

Tamiflu is the drug most people are asking about since it seems to offer some protection to people against the type of flu that has devastated Asian poultry flocks and is spreading to birds in Europe. Bird flu has killed more than 60 people over the past two years.