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Tuberculosis - An Old Disease with a New FaceTuberculosis just won't go away

Japan, a “medium-burden tuberculosis country”

In the past, the prevalence of tuberculosis (TB) in Japan was so high that it was said to be a national threat (in 1943, the TB death rate was 235 per 100,000 people, 150 times higher than in 2015). Then, after the war, the number of cases dropped rapidly, and for a while it was thought that the epidemic was over. However, in 1996-1997, there was a new outbreak of TB cases, and the prevalence rate began to rise again, and continued to do so for 3 years. Japan declared a “tuberculosis state of emergency” to draw attention to the problem. After that, the number of cases finally began to decrease, but tuberculosis had once again gained attention as a “re-emerging infectious disease”. The current prevalence rate is 14 per 100,000 people (or approx. 1 per 7000 people), many times higher than in other developed countries. As this is about the same rate as it was in America in the 1970s, Japan has been designated a “medium-burden tuberculosis country” (Figure 1).

Figure 1: Prevalence rates of tuberculosis in Japan and other developed countries (All tuberculosis, 2015)

Causes of the TB “re-emergence”

Within this “TB re-emergence”, new problems have surfaced.

  1. 1Increase in the number of group infections.
    Among the younger generation, there are many people with no immunity to TB, and late diagnoses and other factors result in increased group infections / infections within hospitals (Figure 2).

    Figure 2: Group Outbreaks: Where does it start? (2003-2014, total cases: 524, cumulative group cases: 710)

    TB group infection is defined as “when a single source of infection spreads tuberculosis to two or more families and 20 or more people”.
    “Social welfare facilities” includes welfare facilities for the elderly, geriatric health service facilities, and facilities for the disabled. “Other” includes places such as restaurants, entertainment facilities, and internet cafes that an unspecified number of people use. Infections that are spread across 2 or more groups are counted multiple times.

  2. 2Increase in the number of severe cases / severe outbreaks
    There are cases of patients becoming seriously ill immediately after catching TB, and cases where TB is only diagnosed after reaching a severe stage.
    What's more, of the patients who are diagnosed with TB and start treatment, 10% will not survive. Among those, half will die within a year of diagnosis (Figure 3).

    Figure 3: Mortality rate of tuberculosis patients over time (1990-2015) (Death within one year of being diagnosed with tuberculosis)

  3. 3Increase in outbreaks among the elderly
    Recently, 70% of outbreaks have been among patients who are age 60 and above. The main reason is that many people in this age group were inflected before or after the war, and with the onset of old age, health problems and other factors trigger the latent TB, causing it to become active.
  4. 4Increase in outbreaks among economically vulnerable members of society
    Recently, there have been a notable number of outbreaks among those who are in socially vulnerable situations, including the homeless, and those who are unable to take proper care of their health.
  5. 5The emergence of multidrug-resistant tuberculosis