Tuberculosis is an infectious disease, meaning that it can be passed from person to person. It is transmitted mainly through coughing.

But the risk of the illness being transmitted is not high. A person would need relatively prolonged contact, usually a matter of hours, with an infected person to be at risk. This is unlike, for instance, measles where a brief contact is usually enough to pass on the illness.

It is true that often several members of one family tend to be affected, but this is because of the prolonged contact between family members.

While TB did affect all classes of society it was more common in those who were disadvantaged. The change in prevalence of the disease is in part due to the introduction of effective treatment but also to the improvement in living standards. The effect of the BCG vaccine is probably relatively small. That is the reason for the new policy introduced by the Department of Health last year to cancel routine immunisation for all school children and to target the vaccine at those who are at greatest risk.

Our 15-month-old son has been desperately ill for a couple of months. He’s had recurrent chest, nose and throat infections with fevers over 40C (104F), and a rash on his torso. He is on ciproflaxin and the latest diagnosis is a suspected bladder/kidney infection, urinary tract infection and pseudomonas. He has an MAG3 scan booked. Can you offer any insight?
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It sounds as if your son’s condition is complicated and this must be really worrying. He may have started off with a viral infection then got a bacterial infection. The doctors have identified pseudomonas, a bacterium, in his urine. Pseudomonas is not common but can appear in children who have been treated with antibiotics for a while because it’s resistant to most of the commonly used antibiotics. So if other bacteria have been killed, pseudomonas may have a chance of emerging. It can be tackled with ciproflaxin, a less common antibiotic, so hopefully your son’s infection should soon settle down.

A diagnosis of a urinary tract infection is made by a urine culture, which involves detailed analysis of a sample of urine. Having diagnosed it, the first investigation to find out why it developed is generally an ultrasound scan. This is to look for any problems with your son’s urinary tract. A MAG3 scan, which can provide more detailed information, is usually recommended for further testing. It involves the injection of a radioactively tagged substance (a tracer).

A camera takes pictures of this substance being processed by the kidneys and will help doctors to identify whether there are any scars, which may have resulted from previous possibly unrecognised infections. They will also be able to look at the way the kidneys drain, pinpointing any obstruction, and/or whether there are any problems with the way the bladder is emptying.

These detailed tests may show that everything’s normal and it might be difficult to pinpoint any cause. But his doctors are likely to want to keep an eye on him in clinic for a time.

Jane Collins is the chief executive and honorary consultant paediatrician at Great Ormond Street Hospital

E-mail Dr Jane at drjane@thetimes.co.uk or write to her at Body&Soul, The Times, 1 Pennington Street, E98 ITT. Please include your name, address and telephone number. She cannot enter into individual correspondence.

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