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Guidance

Appendix 1: Factors that increase vulnerability to TB disease

Published 6 October 2026

© Crown copyright 2026

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This publication is available at https://www.gov.uk/government/publications/tuberculosis-tb-contact-tracing-guidance/appendix-1-factors-that-increase-vulnerability-to-tb-disease

There are a range of factors which can increase one or more of the following in a contact exposed to a case of infectious TB:

  • the likelihood of infection
  • the progression to active TB disease
  • the severity of TB disease

The most important factors are age under 5 years and immune status.

Age

Among younger children:

  • active TB disease is more likely to occur following infection
  • the incubation or latency period is shorter
  • lethal, invasive forms of the disease (such as meningitis and disseminated TB) are more common

Children aged under 16 years who are contacts should therefore be assigned high priority for contact investigation (1).

Medical conditions

Certain medical conditions can increase the likelihood of active TB disease after infection, and contacts with these conditions should be assigned high priority in a contact tracing process. Contacts who are taking certain medications are also more likely to develop TB disease after infection (when exposed or through reactivation of latent disease).

The following are all risk factors for progression to active TB disease after infection:

  • HIV infection, in particular advanced or untreated HIV
  • receiving more than 15 mg of prednisone or its equivalent for more than 4 weeks
  • receiving other immunosuppressive agents, including multiple chemotherapy agents, antirejection drugs for organ transplantation, and tumour necrosis factor alpha (TNF-α) antagonists
  • silicosis
  • diabetes mellitus
  • previous gastrectomy or jejunoileal bypass surgery
  • injecting drug use or excessive alcohol intake
  • chronic renal failure or receiving haemodialysis
  • significantly low weight (body weight at least 10% below ideal body weight)
  • chronic malabsorption syndrome (8)

Pregnancy

Pregnancy may increase the risk of progression from latent TB infection to active TB disease (83). Pregnancy can also make the diagnosis of TB more difficult; TB in pregnancy poses a substantial risk of morbidity to both the pregnant woman and the foetus if not diagnosed and treated in a timely manner (84).

References

See the attached list of references for TB contact tracing guidance.

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