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Cases
= 168Crude Rate
per 100,00 population = 2.9Race/Ethnicity-specific Rates
per 100,000 populationGender-specific Rates
per 100,000 populationTuberculosis (TB) is an airborne disease caused by the acid-fast bacillas Mycobacterium tuberculosis. General symptoms associated with TB are productive cough, coughing up blood, night sweats, fever, and malaise. TB usually affects the lungs, but it can also affect other parts of the body such as the brain, kidneys, or spine. TB bacilli are put into the air when a person who has TB of the lungs or larynx coughs, sneezes, laughs, or sings. The bacilli may then be inhaled by another person. Individuals who inhale TB bacilli may become TB infected, but not develop active disease. Infected persons without active disease do not transmit TB. Some individuals who harbor the bacilli will progress from the stage of TB infection to active disease. These individuals are cases of TB and can transmit TB to others. The bulk of this report concerns itself with cases of TB.
During 1997, 168 new cases of tuberculosis were reported to the Indiana State Department of Health (ISDH). This total was a 17% decrease from the 202 cases reported in 1996. This figure represents the lowest number of cases ever reported to the ISDH. The state case rate is 2.9 cases per 100,000 population. The 1996 U.S. Bureau of the Census, inter-census estimates were used to calculate the rates reported in this document. TB was reported in 46 (50%) of the 92 counties. Cases generally occurred more often in the urban and suburban counties. With the advent of chemotherapy, TB can be treated on an out-patient basis. Chemotherapy has led to a dramatic decline in the number of deaths due to TB disease. During the years 1993-1996, an average of 22 deaths were attributed to TB in the state of Indiana. This figure serves as a stark reminder that TB is still a deadly disease. The number of Hoosiers diagnosed with (Figure 1), and dying from (Figure 2) TB over the past several years, is shown below.
Figure 1.
Figure 2.
As in years past, more males were diagnosed with TB than females. In 1997, males represented 62.7% of the newly diagnosed TB cases. The case rate per 100,000 population was 3.8 for males and 2.0 for females (Figure 3).
Figure 3.
Case rates per 100,000 population by race and ethnicity were 2.1 for Whites, 8.8 for Blacks, 8.5 for Hispanics, and 17.5 for Asians. Although foreign-born persons had the greatest rates of TB, the number of foreign-born persons living in Indiana remains relatively small. For this reason, the rates in this group may be unstable. When foreign-born individuals are excluded from the analysis, case rates stratified by race and ethnicity are as follows: 2.0 for Whites; 7.5 for Blacks; 3.4 for Hispanics; and 1.9 for Asians.
In 1997, 14.3% (24/168) of cases were foreign-born, which means the country of origin was a country other than the US. Among the foreign born, Asia accounted for 45.8% (11/24) of the cases (Figure 4.)
. These individuals came from the Philippines (4), Korea (2), Laos (2), Cambodia (1), India (1), and Vietnam (1). Another 16.7% (4/24) was accounted for by the European countries of Bosnia-Herzegovina (2), Hungary (1), and Poland (1). Latin America also made up 20.8% (5/24) of the foreign born cases represented by Mexico (3), Colombia (1), and Guatemala (1). The remaining 16.6% (4 /24) came from the African countries of Ethiopia (1), Kenya (1), Guinea (1), and Nigeria (1).Figure 4.
In Indiana, the incidence of TB has been higher in individuals over the age of 65. In 1997, 38.6% of the cases were over age 65 with a case rate of 8.8 per 100,000. The incidence of TB decreased with age. Of the total 168 cases reported, 27.2% were age 45-64 with a case rate of 3.8, 25.4% were age 25-44 with a case rate of 2.3, 5.9% were age 15-24 for a case rate of 1.2, and 3.0% were under the age of 14 for a case rate of 0.4. (Figure 5.)
Figure 5.
Five children under the age of 15 were diagnosed in 1997. Four children were four years of age or younger. TB in young children indicates a failure to interrupt the transmission of TB, usually from an adult to a child. Only two of the children had overt signs and symptoms of TB. Two were identified as part of a contact investigation of adult patients with TB. One child was from Bosnia. (Figure 6.)
Figure 6.
Several risk factors are associated with the development of TB disease or progression from infection to disease. The most important of these factors is HIV disease. In 1997, there were four individuals diagnosed with both TB and HIV. Due to the small numbers of individuals diagnosed with both TB and HIV, significant variation in the numbers of cases identified can be expected to occur due to chance alone. (Figure 7.)
Figure 7.
Other risk factors associated with TB are alcohol use, homelessness, illicit drug use (injecting and non-injecting), residence in a long term care (LTC) or correctional facility, or employment as a health care worker (HCW). The breakdown can be see in Table 1.
Table 1. |
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Risk Factor |
Number of Cases |
Percent of Total Cases |
|---|---|---|
| Alcohol use | 13 |
7.7% |
| Homelessness | 7 |
4.2% |
| Illicit drug use | 6 |
3.6% |
| LTC resident | 6 |
3.6% |
| Health care worker | 4 |
2.4% |
| Inmate | 3 |
1.8% |
| No risk factor identified | 129 |
76.8% |
Occupation is another variable used to detect trends. Compilation of these data show that 61.9% of the individuals diagnosed with TB disease were unemployed and 28.0% had employment (Table 2). The "unemployed" category includes retired persons, children, and students. Four health care workers were diagnosed with disease in 1997; three worked in long term care facilities and one worked in a hospital setting.
Table
2. |
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In order for a case of TB to be counted, the case is reviewed by the local health official who is familiar with TB. If the case meets the predetermined case criteria, it is counted as a new TB case. The culture identification of Mycobacterium tuberculosis complex includes three species important in human disease: M. tuberculosis, M. bovis, and M. africanum. The case data in this report are compiled from those reports submitted through the local health departments to ISDH. The cases are verified and categorized as confirmed, clinical or provider diagnosis. "Confirmed" cases are those in which M. tuberculosis has been isolated from a clinical specimen OR M. tuberculosis has been demonstrated in a clinical specimen by a nucleic amplification (NAA) test OR acid fast bacilli (AFB) are seen when a culture has not or cannot be obtained. A "Clinical" case is one in which the individual has a positive tuberculin skin test, an abnormal chest x-ray, symptoms suggestive of TB disease, and improves on anti-TB therapy. The third category is "Provider Diagnosis." This category includes those cases where the physician has determined the patient has TB, is treating with an appropriate drug regimen, and the patient is improving clinically on this regimen. Many in this category include extra-pulmonary TB where laboratory confirmation may be lacking due to the site of the disease and children in whom obtaining specimens is difficult and invasive procedures are not warranted. Table 3 summarizes the reported TB cases by verification criteria.
Table 3. |
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Of the 168 cases reported in 1997, 81.0% (136/168) were pulmonary. Pulmonary cases are of particular concern since these individuals may actively transmit the disease to others. To break this cycle of transmission, appropriate and adequate therapy must be initiated and continued for the duration of the treatment period. ISDH follows the guidelines set by the American Thoracic Society/Centers for Disease Control and Prevention (ATS/CDC) which recommends at least three drugs in the initial regimen. In 1997, 86.9% (146/168) of the cases were started on a drug regimen containing three or more drugs and only 8.9% (15/168) were started on a two-drug regimen. Seven cases were reported at the time of death and no drugs were started. Contact investigations based on the late diagnosis are crucial to protect the survivors.
Drug susceptibility testing is recommended for all cultures positive for TB to detect any resistance to the medications prescribed. In 1997, susceptibility testing was performed on 92.9% (105/113) of initially positive cultures. Multi-drug resistant (MDR) TB is defined as resistance to both isoniazid and rifampin. MDR-TB is of particular public health concern since these two drugs are the most effective medications used to treat TB. If the organism develops resistance to these two medications, they no longer will be effective to treat this disease, thus limiting the arsenal of drugs shown to be effective in the treatment and management of TB. There were no cases of MDR-TB in 1997. Mono-resistant TB is treatable and curable with the standard four-drug regimen. Close and careful monitoring of these patients is necessary to prevent additional drug resistance. Drug resistance was documented in Adams County (Isoniazid, Streptomycin), Hendricks County (Isoniazid), and Howard County (Ethambutol). Depending on the resistance pattern, an extended treatment period may be needed. During 1997, an additional 18 cases diagnosed in previous years were followed by local health departments. The number of drug resistant cases since 1993 is shown in Figure 8.
Figure 8.
Besides drug resistance, non-compliance is another major reason for having to extend the treatment period. The most effective method to assure the patient is complying with the prescribed regimen is to use Directly Observed Therapy (DOT). DOT is a strategy proven to ensure completion of therapy, thereby preventing the emergence of acquired drug resistance. DOT should be considered for all TB patients. Every effort must be made to initiate DOT when the patient is first started on anti-TB medications, especially pulmonary and drug resistant cases. During 1997, 43.1% (72/168) of all cases were on DOT. Of the pulmonary cases, 41.2% (56/136) were on DOT.
Figure 9.
The top priority of TB control and prevention efforts is to ensure completion of therapy in TB patients. Our objective is to have at least 90% of all patients complete an adequate and appropriate course of therapy. Because completion data are gathered at the end of therapy, the current data are for those patients who initiated therapy in 1996The state completion rate was 91.7% during the first half of the year and 93.5% for the second half. Because Marion County includes the largest city and reports such a large number of cases, they submit their own reports to the State and to CDC. Separate reporting by Marion County ensures that the State data are not severely skewed. The Marion County completion rate was 82.4% during the first half of the year, and 95.8% for the second half of the year. Trend data are shown in Figure 10.
Figure 10.
The second priority in TB control and prevention is to identify those individuals who are infected with TB and could benefit the most from preventive therapy. Those individuals who have had recent contact with a known TB case, individuals who have converted their skin test within the last two years, individuals from high risk groups, and individuals whose immune system may be compromised for any reason will derive the greatest benefit from early detection and preventive therapy. The best means of identifying exposed and infected individuals is to perform a complete and thorough contact investigation. During 1997, 88.0% (95/108) of the State pulmonary cases had contacts identified. Of the State cases with contacts identified, the median number of contacts identified was 8 with a range of 1-202. For Marion County, the median number of contacts was 7 with a range of 1-109. The median number of contacts tested was 8 for the State and 7 for Marion County with respective ranges of 1-186 and 1-68. As a result of the follow-up, two of the contacts were found to have active TB disease. Based on national estimates, each infectious case averages nine contacts, 21% of whom are infected, and 1% found to have disease when identified as a contact. Of the 8.2% in Indiana identified with TB infection, 52.7% were started on preventive therapy. Children under the age of 15 represented 14.1% of the infected contacts and 94.6% were started on preventive therapy.
Completion of preventive therapy rates for contacts is tracked by age. During the first half of 1996, the State completion rate for contacts under the age of 15 was 83.3% and increased to 100% the second half of the year (Figure 11). For Marion County, the rates were 44.4% and 33.0% respectively. For those age 15 and older, the State completion rates were 79.1% and 82.9% (Figure 12). For Marion County, the rates were 78.6% and 77.8%.
Figure 11.
Figure 12.
Figure 13 gives an overview of where the TB cases occurred geographically within the state. The numbers represent the number of cases in each county with the number of drug resistant cases in parentheses. TB was reported by 46 of the 92 (50%) Indiana counties. Drug resistant cases were reported in three counties.
Reported Number of TB Cases by County, 1997
Figure 13.
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