Biggest TB Investigation
In Dutch Health
History Begins

From Patricia Doyle, PhD
The largest tuberculosis (TB) investigation in Dutch history begins in Zeist on Mon 31 Jan 2005. 5 percent of the 15 000 people undergoing tests are expected to have been infected with the bacteria.
An employee of a C1000 supermarket in the central Dutch city was diagnosed with a very infectious form of TB in November 2004. Initial tests confirmed that the 25-year-old man's entire family and 40 of his 79 colleagues have also been infected. Zeist City Council and the health authority GGD Midden-Nederland decided to examine every customer who shopped at the supermarket between 18 Nov 2004 and 1 Jan 2005 based on a telephone survey. The GGD expects to test 15 000 people from the municipality this week [1st week of February 2005].
75 percent of the C1000 customers urged to report for an examination will undergo Mantoux tests. The procedure involves testing exposure to TB by injecting diluted tuberculin under the skin. For people older than 60, lung x- rays will be taken in a mobile health clinic.
TB doctor and the coordinator of the KNCV Tuberculosis Fund, Vincent Kuyvenhoven, told newspaper De Volkskrant that it is reasonable to expect 5 percent of the people examined will be infected with TB. "But it could also be 10 percent," he said.
Kuyvenhoven -- who said the investigation was the largest of its kind in the Netherlands -- explained that the infection rate is dependent on many factors. This includes how closely the infected supermarket employee came into contact with customers.
ProMed Mail
It is not stated in the above posting whether the index case had laryngeal tuberculosis or not. It has been generally accepted that laryngeal TB is the most highly infectious form, but since most cases are associated with far advanced open cavitary pulmonary disease, the infectivity of laryngeal TB alone has not been clearly proven. In 2 patients with laryngeal TB without pulmonary disease, no evidence of intrafamilial spread was found, suggesting the laryngeal disease in itself may not be so infectious (1). This moderator has been involved with a similar case in which isolated laryngeal TB was diagnosed, and despite a delay in making the diagnosis, no family and hospital spread was found.
Having a positive Mantoux skin test for TB, assuming that the test was performed and read appropriately, reflects previous exposure to TB, not necessarily active infection at that time. Individuals with a positive skin test (2) have an approximately 10 percent chance of developing active tuberculosis in their lifetimes, 5 percent in the 1st 2 years and 5 percent afterwards. The risk of reactivation can be as high as 10 percent per year in AIDS patients.
It is not clear how an estimate of 5-10 percent skin test reactivity after this exposure for those shopping in the store is suggested, as infectivity correlates with degree of exposure. Family and close friends having a high degree of skin test reactivity (it is likely the case that none of them have been found to have overt infection) does not necessarily suggest a high degree of transmission to much more casual contacts in less confined areas.
It was Robert Koch in 1891, following his identification of the human tubercle bacillus, who felt that he could develop a cure for TB using a filtrate of killed organisms (3). This was not to be the case, but testing was found to be used as a diagnostic test, first observed by European veterinarians (4).
1. Horowitz G, Kaslow R, Friedland G: Infectiousness of laryngeal tuberculosis. Am Rev Respir Dis 1976; 114:241-44.
2. Lutwick LI: Tuberculin skin testing. In, Tuberculosis, A Clinical Handbook. Lutwick LI (ed), Chapam & Hall, London, UK, 1995.
3. Koch R. Weitere mitteilungen uber ein Heilmittel gegen Tuberculose. Dtsch Med Wschr 1891; 17:101-102.
4. Snider DE: The tuberculin skin test. Am Rev Respir Dis 1982; 125 (Suppl): 108-18. - Mod.LL
Patricia A. Doyle, PhD
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