UPDATE 1-Calls for oversight grow as US meningitis death toll mounts

* Lawmakers seek tighter regulation of compounding companies

* Outbreak has sickened 124 people in 10 states, killed 12

* May take to early Nov. to identify all stricken in Tennessee

(Updates figures, adds quotes)

By Tim Ghianni

NASHVILLE, Tenn., Oct 10 (Reuters) - The toll from the outbreak of fungal meningitis tied to contaminated steroid shots that has killed 12 people in the United States was expected to grow on Wednesday, raising pressure for stricter oversight of a largely unregulated corner of the pharmaceutical world.

On Tuesday, four more deaths were reported and Florida became the latest state to report at least one death linked to the illness in a widening health scare.

Since the Sept. 25 recall of three lots of a steroid produced by a Massachusetts company, the outbreak has spread to 10 states and infected 124 people, according to state health departments and the Centers for Disease Control and Prevention.

Leading U.S. House and Senate lawmakers from both parties on Tuesday asked federal health officials for briefings on the outbreak as a first step toward possible legislative action to strengthen federal drug safety regulations.

Oversight committees in both the Senate and House hope to learn more about the outbreak before Oct. 12 from staff members of the Food and Drug Administration and the CDC, aides said.

In five states - Tennessee, Michigan, Maryland, Virginia, and Florida - the outbreak has claimed lives, with the latest victim a 70-year-old man in Florida.

As many as 13,000 people received the injections to relieve back pain and other complaints and are at risk of infection, the CDC said, although the number ultimately stricken is likely to be far fewer.

For the first time on Tuesday, Tennessee state health officials gave an estimate of the rate of infection among those patients who received injections from the recalled steroid supplies. Approximately 5 percent of patients treated with the suspect medication in Tennessee have contracted meningitis, said Dr. David Reagan, chief medical officer for the Tennessee Department of Health.

"We expect that most people who were exposed to this will not develop a fungal infection," Reagan said.

The rate of infection overall is not known.

Meningitis is an infection of the membranes covering the brain and spinal cord. Symptoms include headache, fever and nausea. Fungal meningitis, unlike viral and bacterial meningitis, is not contagious.

The outbreak has highlighted a gap in regulation of so-called pharmacy compounders, which are facilities that take drug ingredients and package them into medications and dosages for specific clients.

The federal Food and Drug Administration regulates only the ingredients and not the compounders, which are subject to a patchwork of state oversight.

George Cary, whose wife Lilian Cary is one of three women to die in the outbreak from Michigan, said Tuesday that Americans have a strong belief in their medical and political system and the outbreak should be a wake-up call to the nation.

"We don't have expectations of a faulty regulatory medical system that allows these types of mistakes to be made," Cary told reporters on his front lawn after a memorial for his wife. "So perhaps the message is, wake up America."

Some of the thousands of people exposed may have to wait anxiously for weeks because the incubation period of the disease is up to a month, health experts said.

In Tennessee cases, officials said they have found the average incubation period to be 16 days, but they caution that it could range from six to 42 days for their patients.

Tennessee believes they could still see new cases into the early part of November, though that could change as more information is collected, officials said.

The potentially tainted steroid vials, which have been recalled, were shipped to 76 facilities in 23 states, the CDC has said.

Tennessee has been the hardest hit state, with six reported deaths and 39 cases of meningitis, followed by Michigan with three deaths and 25 cases, Virginia with one death and 24 cases and Maryland with one death and eight cases.

The other states with cases are Indiana (15), Florida (6), Minnesota (3), North Carolina (2), Ohio (1) and New Jersey (1).

(Additional reporting by David Morgan, Susan Guyett and Meghana Keshavan; Editing by Lisa Shumaker and Claudia Parsons)