Overview
Tuberculosis (TB) is a bacterial infection caused by Mycobacterium tuberculosis. Most cases reported in New Zealand are in people from overseas. TB can remain inactive (latent TB), sometimes for many years, before it becomes active. When TB progresses from latent infection to active disease it usually affects the lungs, but may affect any organ of the body.
Introduction
Infants, young children, and children with weakened immune systems are at the highest risk of developing the most severe forms of TB such as TB meningitis (infection of the layers that cover the brain) or disseminated (miliary) TB (affecting the lymph nodes and other tissues).
Tuberculosis (TB) notification rates in New Zealand are around 7 - 10 per 100,000 a year, higher rates of disease when compared to many other developed countries. This may be attributed to socioeconomic deprivation, and immigration from high-incidence countries. Over two-thirds of all TB cases in New Zealand are in foreign-born individuals. The highest rates of disease are seen in individuals living in urban areas, particularly Auckland and South Auckland, and in people of non-European ethnicity.
Transmission
The bacteria are passed by inhaling droplets from an infected person through coughing, sneezing or spitting. One person with active tuberculosis can infect more than 1 in 4 of their close contacts, therefore, people in close contact with a known case of TB are at high risk of infection.
Most children are infected from an infectious adult within their own immediate or extended family. People residing in close communities and institutions, including refugee camps and immigration centres, prisons, rest homes and mental health facilities, are also at risk if exposed to an infected person. Overcrowded housing and poverty increases the spread of TB.
Symptoms
People with TB may not have any symptoms. When symptoms are present, they include fever, prolonged cough, coughing up thick or blood-stained phlegm or blood, swollen glands, chest pain, night sweats, weight loss or poor weight gain, anorexia (lack of appetite) and malaise (tiredness).
Treatment
Active TB is treated with a combination of long term antibiotics that must be taken regularly for around six months.
Risks
About half the people with active TB disease will die if they do not receive treatment.
Children are more likely to progress from latent TB to active disease than adults. They also have a higher risk of developing the most severe forms of disease. Older people are also at risk of severe disease. Although uncommon, severe bleeding (haemorrhage) can result from damage to the lungs in pulmonary TB patients.
The tuberculosis strain may become antibiotic resistant, particularly if the full antibiotic course is not taken.
People regularly exposed to cattle, deer, possums and certain animal products are at risk, however, occupational contact as a risk factor is poorly documented. TB occurs in about 2% of people with HIV infection in New Zealand. Congenital TB (acquired before birth) is rare. Breastfeeding is not a risk factor and does NOT pass TB onto the infant.
Prevention
In New Zealand, neonatal BCG vaccine should be offered to infants who are at risk of infection.
Doctors are legally required notify the Medical Officer of Health of any suspected or proven diagnosis of active TB or reoccurrence of TB. However, they are required to obtain permission from people who have a latent, inactive TB infection prior to reporting these cases.
Countries with high TB rate include: most of Africa, much of South America, Russia and the former Soviet states, the Indian subcontinent, China, including Hong Kong and, South East Asia (except Singapore).
Children with active TB are excluded from school until effective antibiotic treatment has started, compliance with treatment is established and any symptoms have decreased.
Healthcare staff and students from high incidence countries should be screened for TB infection before starting work or study. Those at high risk of TB exposure are monitored annually.
