Rate of infection edging up after 50 years of decline

A DOCTOR WRITES:THE OUTBREAK of tuberculosis (TB) in a Cork school is a reminder that the infectious disease is still endemic in the Republic, albeit at levels far below the 7,000 cases diagnosed annually in the 1950s.

The latest figures suggest 400-500 new cases are identified here every year. However, after about 50 years of declining TB rates, figures from the Health Protection Surveillance Centre show the rate rose from 9.7 cases per 100,000 population in 2000 to 11.3 per 100,000 in 2007.

It is estimated that about 1.8 million people worldwide died from TB in 2008, mostly in the developing world.

The World Health Organisation’s Stop TB Strategy aims to reduce the global burden of TB disease by half in 2015 relative to 1990 levels.

Caused by the bacterium mycobacterium tuberculosis, TB is spread by droplets in the air. A person with infectious TB can expel TB germs into the air when they cough or sneeze. People in the surrounding area can then inhale these TB germs.

Each person with active infectious TB infects on average 10-15 people a year. But many people who become infected never go on to develop the disease. Instead, the bug lies dormant in the body, and the person is said to have “latent” TB.

People with this form of TB cannot infect others but, when diagnosed, are treated to prevent the reactivation of the microbe in their own bodies, which would lead to full-blown infection.

The symptoms of full-blown TB are varied and depend on the organs affected. For the lungs, typical symptoms include cough, sputum which may be flecked with blood, tiredness and loss of appetite. Weight loss is also common and the patient may have a fever.

TB can infect bones in the spine and may infect the lining of the spinal cord, leading to TB meningitis.

How are people screened for the disease? A skin test called a Mantoux test is carried out along with a chest X-ray.

Those with symptoms who are suspected of having an active infection will have their sputum analysed in a laboratory looking for the microbe’s presence.

BCG immunisation offers some protection from the disease. It is given to newborns in maternity hospitals and to unprotected contacts of people who develop TB.

The multiple-drug therapy is needed to combat drug-resistant TB. Treatment involves taking four antibiotics for two months followed by two drugs for a further four to seven months.

There is a growing trend worldwide for treatment to be directly observed by a healthcare professional to combat the possibility of incomplete treatment which, apart from the patient not being cured, contributes to the development of drug-resistant TB.

The Irish Thoracic Society favours introducing a focused screening programme for TB. This would concentrate on social groups known to have a higher prevalence of TB such as the homeless, prisoners, those with HIV infection and immigrants from certain countries.