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What is TB?
Like a cold or flu, Tuberculosis is an infectious disease that spreads through the air. Someone sick with pulmonary (lung) TB is infectious to others; each cough spreads TB germs and you only need inhale a few to become infected yourself. A person infected with TB doesn't necessarily get sick with TB, the immune system "walls off" the TB cells and they lie dormant, but if the immune system is weakened, the chances of getting sick with TB get greater.
Any one can get TB infection , but the chances of becoming ill with tuberculosis are greater if you are:
Up to 50 years ago, there were no drugs for TB. Back then we didn't have the number of people travelling all around the world for business or foreign holidays. Additionally, the number of refugees and displaced people in the world is increasing, and homeless people in industrialised countries are at risk. In 1995, approximately 25% of London's homeless were reported to be infected with TB. These figures compare to overall prevalence of 13% in the United Kingdom. Prevalence of TB infection in prisons is much higher.
TB disease develops slowly. Fever, night sweats, coughing, spitting up blood, and weight loss are all symptoms that might suggest TB illness, but people with HIV might have these symptoms for a number of other reasons.
A skin test (called a "Heaf" or PPD test) may identify if you are immune to TB infection (ie, already exposed to it or still protected by immunisation). As people with HIV are more likely to develop active TB, some are offered a course of treatment for TB after a positive skin test : this is standard practice in the US, but less likely in the UK. Pulmonary TB is diagnosed by chest X-ray and sputum (phlegm) analysis. If you have TB, doctors will want lots of sputum - they get very excited over it! If TB bacteria show up under the microscope, you are likely to still be infectious.
If you have been found to have TB disease, your doctor will notify the Public Health Laboratory Service who monitor diseases like TB (and HIV) to see how they move around the population.
TB is one of the so-called "notifiable diseases" and your doctor is bound by law to notify a health officer at your local authority. Your doctor may need to get in touch with people you have been in contact with, like family, people you live with or see regularly. You may be asked to give a list of these people.
A combination of drugs is taken between 9 and 12 months. About 2 weeks after starting treatment, the patient is no longer infectious to others. To ensure patients complete treatment, they may be placed on "DOTS" - Directly Observed Treatment Short course - someone watches while TB drugs are taken three times each week until the course is finished. Treatment options for people on HIV drugs as well are more complex and may require a change of HIV therapy or stopping it altogether while TB is being treated.
People with active TB should be nursed in single rooms, not open hospital wards, with negative pressure so that air is gently sucked out of the room and bacteria cannot escape into the rest of the hospital.
The BCG vaccination can be given to people who are HIV negative. School children have traditionally been given the BCG in the UK and this reduced the number infected with TB in childhood. This vaccine has variable effectiveness, only gives about 10 years protection and must not be given to people with HIV infection. A new born child of an HIV positive mother should not be given BCG vaccination until (and only if) tests prove the child is HIV negative.
A new vaccine is being developed at Oxford University, the first for TB to enter clinical trials in over 80 years.
Drug-resistant TB arises when patients don't take all their drugs regularly for the required period because they start to feel better. Multidrug-resistant TB (MDR-TB) is TB resistant to at least isoniazid and rifampicin - the two most powerful anti-TB drugs. MDR-TB is treatable with up to two years of extensive chemotherapy that is often more than 100 times more expensive than treatment of drug-susceptible TB.
A survey from London hospitals has shown that patients who are diagnosed with both HIV and tuberculosis (TB) are among the most difficult group to treat. There are now more cases of TB in London than anywhere else in Europe, with two deaths and 50 new cases every week.
The study looked at 188 London patients diagnosed with TB and HIV between 1996 and '99. Four out of 10 had no idea they were HIV positive when diagnosed with TB. Most had advanced HIV illness: their average CD4 count was 94, and 39 per cent fell ill with Aids while they were on TB therapy. The study's authors recommended that HIV/TB co-infected patients with CD4 counts under 100 should be started on HIV therapy immediately - regardless of the risk of side effects.
In practice, however, over half were not prescribed HIV therapy while on TB treatment, because patients receiving TB and HIV therapy together were almost twice as likely to experience bad reactions to HIV drugs. The women in the group were four times more likely. This meant that either the TB or the HIV therapy had to be stopped. Bad reactions to TB drugs mainly occurred in the first two months of therapy, so the study's authors suggested that HIV therapy could be delayed for two months in all but the most immune-compromised patients
A US study has shown that, alone among Aids-defining infections, TB has not become less common since 1996. A Spanish study has shown that TB/HIV co-infected patients with CD4 counts under 100 are much more likely than others to develop multi-drug-resistant TB. And a New York study says that HIV/TB co-infected patients are four times more likely to fail their therapy, and recommends TB treatment should be maintained for as long as a year.
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