Most TB outbreaks were caused by exposure of many people to
tuberculosis bacilli due to delayed detection of initial cases who had long-lasting severe
coughs and excretion of massive
tuberculosis bacilli. They were also affected by several other factors, such as socio-environmental factors of the initial case; time and place of
infection; and host factors of the infected persons such as immune status, infectivity, and/or pathogenicity of the bacilli. In this symposium, we learned the seriousness of
infection and disease among immune-suppressed groups, special environmental factors with regard to the spread of
infection, disease
after treatment of
latent tuberculosis infection, diagnostic specification of IGRA, and bacteriological features including genotyping of the bacilli. We reaffirmed that countermeasures for the case are important, but outbreaks can provide excellent opportunities to learn important information about
infection,
disease progression, etc. 1.
Tuberculosis outbreak in a
cancer ward: Katsuhiro KUWABARA (Division of
Respiratory Diseases, National Hospital Organization Nishi-Niigata Chuo National Hospital) There was an outbreak of
tuberculosis in a
cancer ward of a highly specialized medical center. Outbreak cases included eight hospitalized patients and two medical staff members over a 1.5-year observation period after initial contact. Three immune-compromised patients including the index patent died of
cancer and
tuberculosis. Community hospitals and highly specialized medical centers, such as
cancer centers, should carefully prepare a proper system to prevent nosocomial transmission of
tuberculosis. 2. Sixty-one cases of TB exposures in hospital settings and contact investigations of the hospital staff, with special reference to the application of QFT: Hiroko Yoshikawa NIGORIKAWA (The Division of
Infectious Diseases, Tokyo Metropolitan Health and Medical Treatment Corporation, Toshima Hospital; present: Division of
Infectious Diseases, Tokyo Teishin Hospital), Toru MORI (Research Institute of
Tuberculosis, Japan Anti-
Tuberculosis Association) The index case was a patient who was admitted to a general hospital where she was treated with pulsed
corticosteroid therapy and then put on a
respirator. Soon after, she developed
tuberculosis (TB) and died. Immediately after her death, the healthcare workers who had close contact with the index case were given the QuantiFERON TB
Gold (QFT) test, which indicated that all staff except one were negative. However, a QFT test administered eight weeks later had a positive rate of 18.6%. Subsequently, a total of five workers, including a doctor, nurses, and radiology technicians, developed TB. The bacterial isolates from five of them exhibited an RFLP pattern identical to that of the index case. These secondary cases of TB included a case who had contact of less than 5 minutes, a case whose QFT was negative ("doubtful" in the Japanese criterion of the QFT), and a case who was QFT-positive but declined to be treated for latent TB
infection (LTBI). No other workers nor hospitalized patients developed TB. The healthcare worker contacts were further examined with the QFT 6, 9 and 12 months after the contact. The QFT results revealed four additional positive reactors and four "doubtful" reactors who were indicated for LTBI treatment. Among them were seven subjects who turned positive six months after the contact. TB prevention in hospital settings and contact investigations were discussed with the hospital staff, with special reference to the application of QFT. 3. Summary and issues of concern relating to a
tuberculosis outbreak in a prison: Mitsunobu HOMMA, Takefumi ITOH (Department of Respiratory Medicine, Akita City Hospital) We report a
tuberculosis outbreak that occurred in a prison in the spring of 2011, resulting in 11 cases of active disease and 40 cases of
infection. The primary cause of the outbreak is thought to be the delay in identifying the index case, where the screening result interpretation might have contributed to the delay. However, we also speculate that environmental factors, such as occurrence in the closed space of a prison, inmates spending long periods living together, inmates staying in their rooms due to the cold winter, and poor ventilation in the prison factory, all contributed to accelerating the spread of the
infection. Both the QuantiFERON TB-2G (QFT)-positive rate and disease incidence were higher among the close contact group, and there were no cases of
tuberculosis among QFT-negative individuals, proving the utility of QFT screening in contact surveys. Genetic testing for Mycobacterium tuberculosis is a useful method for studying outbreak cases. In the present case, it led to the discovery of an unexpected route of
infection, reaffirming its importance. This outbreak occurred among a particular population with whom it was difficult to deal and it occurred under unique circumstances. In fact, there were various obstacles to overcome, the most important of which was to ensure the three organizations involved (prisons, health centers, and hospitals) worked together closely, sharing accurate, real-time information. 4. Environmental factors, treatment for
latent tuberculosis infection and molecular epidemiology relating to an outbreak of
tuberculosis: Makoto TOYOTA (Kochi City Public Health Center), Seiya KATO (Research Institute of
Tuberculosis, Japan Anti-
Tuberculosis Association). The ventilation rate within the room of a junior high school was analyzed using
sulfur hexafluoride (SF6) as the tracer gas. Low ventilation of the room contributed to the massive outbreak. The risk of active
tuberculosis was reduced by 81.0% with treatment for
latent tuberculosis infection, compared with that without treatment. Delayed reactivation of
tuberculosis was observed among patients treated with
isoniazid for
latent tuberculosis infection. Molecular epidemiology can provide insights into the process of
tuberculosis transmission, which may otherwise go unrecognized by conventional contact investigations. Additionally, it can play an important role in identifying places of
tuberculosis outbreaks and routes of transmission in a contact investigation.