Do health care workers need to wear masks when caring for patients with pulmonary tuberculosis?

Outbreaks of hospital acquired tuberculosis (TB) in the 1990s, some of which affected staff, highlight the fact that TB still poses a risk to health care workers (HCWs). This risk is best minimised by the primary controls of early identification and treatment, good infection control practice such as early isolation, patients covering mouths when coughing, and engineering controls such as negative pressure isolation. There is no direct evidence to prove that the use of respiratory protective devices has prevented HCWs from acquiring TB, but modelling has shown that environmental controls are not enough to prevent exposure. Masks that filter aerosols (including TB) and have at least 95% efficiency of filtering particles 0.3 micron in diameter can reduce exposure. Environmental controls in the United Kingdom (UK) do not (always) include a specified minimum number of air-changes per hour or negative pressure. Therefore it seems reasonable to advise that HCWs should use masks as advocated by national guidelines for high risk procedures. Masks are also of value when entering any body cavity or dissecting any viscus/organ in which TB is suspected, as in the necropsy room or operating theatre. This is recommended in current guidelines from the United States but not those from the UK.