September 13, 1996

New mask holds back rising threat of tuberculosis

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Dr. Ban Mishu Allos

New mask holds back rising threat of tuberculosis

The rising incidence of tuberculosis in the United States has made physicians reconsider the Centers for Disease Control's prediction that the disease can be eradicated by the year 2010.

Doctors at Vanderbilt University Medical Center treated 24 cases of tuberculosis in 1995 and have treated 14 cases of the mycobacterial infection so far in 1996.

These numbers lead to concern that an outbreak may occur here like the recent incident in Maine, where 697 people were infected by one very contagious patient. A description of that outbreak was published last month in the Annals of Internal Medicine.

When a patient comes in to VUMC with chronic cough, fever, or weight loss, "a diagnosis of tuberculosis should be considered," said Dr. Ban Mishu Allos, assistant professor of Medicine and former Epidemic Intelligence Officer at the CDC. "As soon as it is suspected, the patient should be put into isolation so the risk of transmission is minimized."

In the 19th century tuberculosis was the number one cause of death in this country, with 1 percent of the population dying of the disease each year. Today, it continues to show remarkable durability, Allos said.

"What is really scary is that we now have strains that are resistant to our first line agents, strains that are resistant to our second line agents, and some strains that are resistant to all known anti-mycobacterial agents."

The main contributor to m.tuberculosis' resistance to drugs is infected people who take their medicine inconsistently or begin taking it and then stop. The regularly prescribed treatment is isoniazid prophylaxis. Because m.tuberculosis can become resistant if frequent breaks in treatment occur, patients must take their medication consistently, Allos said.

"The health department will provide Directly Observed Therapy (DOT) for patients with active tuberculosis who have not been compliant with their medication. A public health nurse gives the patient the medicine and watches them swallow it either at the health department or at the patient's home. Some people think that everybody with active pulmonary TB should be on DOT," said Allos.

Currently, Directly Observed Therapy is recommended only for those patients who are considered non-compliant and potentially contagious.

The other weapon in the tuberculosis control arsenal is prevention. Here at VUMC employees are required to wear special masks to enter respiratory isolation rooms. This is meant to reduce the chances of employees spreading the mycobacteria in the hospital.

Taking care of patients in respiratory isolation used to be a chore for hospital personnel. The masks used to protect them from airborne diseases were bulky and looked intimidating to patients. As a result, many people did not wear them and instead used regular sterile masks which were not very effective at keeping out the mycobacterium.

VUMC's Department of Institutional Safety is working to make respiratory isolation safer by introducing new respirators that resemble the masks worn in the OR, but filter out most airborne contaminates. The Racal N-95 respirators are less bulky and are specially fitted for each person.

Dyan Martin, campus safety officer, fits employees for the new masks.

"These masks filter out many more airborne diseases than the OR masks. They are also easier to carry than the old ones so hopefully people will be willing to stick them in their pockets and use them," she said.

The process of having a respirator fitted is short and fairly simple. After molding the mask to the contours of the face, Martin sprays a fine mist of saccharin into a hood. If the person being fitted can taste the saccharin the mask must be adjusted or another size chosen. The process is repeated until a proper fit has been attained and the person can no longer taste the saccharin.

"Some people don't want to take the three minutes to be fitted with the new mask, but once they get the new one they will be able to wear it for a longer amount of time and slip it in their pockets," said Martin.

The hospital has also taken steps to ensure that all employees who work in the hospital take a tuberculosis skin test every year. Those with high exposures to patients with infectious or pulmonary diseases should be tested every six months, said Allos.

The goal of these precautions is to prevent an outbreak of tuberculosis at VUMC like the one that Allos observed in a small town in Maine. A man in a local shipyard contracted the disease which spread to 697 of the 9,898 people tested. Though only 21 active cases of the disease were treated, eight months had lapsed between the onset of the source patent's illness and the proper diagnosis and treatment.

"This man sought medical care repeatedly but the doctors who saw him didn't think about tuberculosis. They even did a chest x-ray which was read by the radiologist as tuberculosis," said Allos, "They sent him home and told him to wear a mask to work."

The outbreak was not discovered until the roommate of the source patient went to a private physician who made the correct diagnosis.

"One mistake was not accurately diagnosing the patient's illness. The other mistake was that the health department did not test enough people quickly enough. Later, when hundreds of newly infected people were identified, more than 50 percent did not complete isoniazid prophylaxis.

"As a result this outbreak lasted for three years," said Allos.