On May 27, the test result showed a positive sign of contagious TB.

At that point an investigation began by HSA to identify frequent contacts of the patient. This included notification and testing of all family members residing in the home and co-workers. During the investigation, it was discovered that the patient was a regular rider of the Modesto BART Express Commuter Bus during the months of April and May 2001.

On June 14, 2001, Laidlaw, Inc., transit contractor with the City of Modesto, was notified by HSA of the incident. Laidlaw contacted the City of Modesto Transit Division immediately following notification.

During the period between June 14 and July 5, HSA continued its investigation. Six bus drivers from Laidlaw were tested. One driver tested positive on a skin test yet recently tested negative following an x-ray examination. This means that although the driver is considered "latent" or a carrier of the TB germ, he is not contagious at this time.

On July 5, representatives from the City of Modesto and Laidlaw met with HSA. Because of the chance of exposure, HSA officials felt it was advisable to test fellow passengers on the BART Express. Individuals at risk are those that rode with the contagious passenger for at least 8 hours. Although the bus trips are only within a 2-3 hour time frame, HSA and the City felt that because of a consistency in ridership during the time period of exposure, all regular passengers should be tested. A plan was developed to notify the passengers.

Because ridership on the BART Express is the lowest on Fridays and Mondays, the passengers were notified on Tuesday, July 10.

On July 10, two health officials from the HSA and two staff members from the City of Modesto Transit Division rode the two afternoon BART Express buses for the trip from the Dublin BART station to Modesto. During this time, HSA and City staff informed approximately 57 riders of the situation and answered any questions. The health officials handed out information about TB. City staff gathered names of riders who rode the buses during the period of April and May.

This morning (July 11), testing of current passengers were offered prior to bus departures for Dublin. Approximately 30 individuals completed the testing. Additional testing by HSA will be available on Friday, July 13 for those passengers that missed this first opportunity.

Currently, City Transit Division staff is preparing a list of passengers that rode on a regular basis during the time the contagious person rode. At-risk passengers on the list that are not tested at the BART Express bus stop will be sought out by the HSA. Occasional riders (those without bus passes) are not considered by the HSA to be at risk of contracting the TB germ. Again, individuals at risk are those that rode with the contagious passenger for at least 8 hours.

Passengers riding the City's BART Express are not at risk at this time as a result of the exposure in April and May. No passengers of any other route on the City's MAX system have ever, at any time, been at risk as a result of this incident.

The potential for exposure to the TB germ is unique to the BART Express bus and was limited to the relatively short window of exposure this spring. Unlike non-commuter routes, passengers on the city's BART Express bus ride together for 2 ½ to 3 hours each day for several consecutive days at a time. On non-commuter routes passengers do not ride together for so many hours and days. Only persons exposed to contagious tuberculosis for several hours are considered to be at risk for infection.

People who have a positive reaction to the skin test, but who do not have contagious TB, cannot spread the germs to others. Although active, contagious tuberculosis can be serious if left untreated, early detection and treatment are very effective in eliminating the disease.

Some positive skin test results are anticipated, since approximately 7% of the general population typically test positive for a number of reasons. Only 10% of those with a positive skin test actually develop active, contagious tuberculosis. Further testing, including a chest x-ray and phlegm specimen, is necessary to determine if an individual has contagious tuberculosis.

The City will continue to work with the Health Services Agency to ensure the public health is protected. More information about tuberculosis is available at www.cdc.gov. Click on "Health Topics" and then "Tuberculosis".

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