Indoor infection in a modern building

Area of Science:

• Epidemiology
• Environmental Health
• Infectious Disease Control

Background:

• Tuberculosis (TB) outbreaks, historically uncommon, are resurging in Japan.
• An investigation was prompted by four TB cases among employees in a modern Tokyo office building between May 1979 and June 1980.

Observation:

• The initial infectious case, a male with positive smears and lung cavities, likely transmitted TB for a year.
• Contact tracing identified 16 secondary TB cases among 99 individuals, predominantly on the same floor as the index patient.
• No TB cases were found in employees of a different company occupying the same building.

Findings:

• Secondary TB attack rates were highest among those working on the same floor as the index case.
• Proximity of secondary cases' desks to the index case suggested close-contact transmission.
• Elevated carbon dioxide levels (1,000-2,000 ppm) indicated inadequate ventilation, especially when closed for energy conservation.

Implications:

• Insufficient ventilation in modern buildings can facilitate indoor transmission of tuberculosis.
• Energy conservation measures, if compromising ventilation, pose a significant public health risk.
• This case underscores the importance of maintaining adequate ventilation for controlling infectious disease spread in occupational settings.