Think of latent meaning “dormant” or “sleeping”. TB germs can live in your body without making you ill. This is called latent TB infection, which is non-infectious to others. Indeed this is very common and in most cases it is nothing to worry about, as the patient probably won’t ever become sick. According to the World Health Organization (WHO), one in three people of the world’s population already has latent TB infection. That simply means that they have breathed in the TB germ at some point in their lives, but the body’s natural defences make the germ “sleep” effectively, making it inactive.

However, sometimes the TB germs “wake up” and break away from this trap set by the body’s natural defences. When this happens the “actual” TB disease can develop. Some doctors may think it wise to give a patient who is found to have latent TB infection medicines to make sure the patient doesn’t become ill as a precautionary measure. It is very routine, especially for people who are HIV-positive.

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If you have latent TB infection then you will not feel ill, have symptoms and won’t be infectious. But if you develop active TB disease then you may feel weak and tired. You might start to lose weight. If you have active TB disease you may also lose your appetite. You might develop a fever, and possibly night sweats. When TB is in your lungs (pulmonary TB) you may get any combination of the symptoms mentioned above, but also accompanied by a cough. You may have chest pain and might be coughing up some blood or blood-stained phlegm (sputum). You may also feel short of breath. Symptoms vary, depending on what part of the body is affected. Left untreated, these symptoms could get worse and put you, and potentially your family, especially young children, in danger.

The symptoms of TB can manifest in a variety of ways, but few people will have all of the symptoms mentioned here. It is important if you develop these symptoms that you see a doctor, particularly if you have had TB before, or are known to be latently infected, and you are HIV-positive. If you are taking TB medication and these symptoms develop you should tell your TB doctor or nurse. The TB medicines you are taking may not be working properly, and they may need to change them.

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Absolutely anyone can be latently infected with TB. But some groups of people are at a higher risk of developing active TB disease. These include:

people with poor nutrition;
people who smoke;  
people who are homeless;  
people who come from countries where  there is a high incidence of TB;
people who work in mines;
people in nursing homes;
people who are prisoners;  
people with alcohol dependency;  
people who are intravenous drug-users;  
people with medical conditions such as diabetes or certain cancers;
people living with HIV or AIDS;  
people living in poor and overcrowded  living conditions.

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You may have heard of multidrug-resistant tuberculosis (MDR-TB), but what is it? MDR-TB is just ike TB as it is explained above, it has the same symptoms and you get it in the same way as TB. It is no more infectious than common TB. Indeed, it very similar in every way except that the tablets usually used to treat common TB don’t work as well and different TB tablets and injections need to be used for two years. MDR-TB is very serious as it is harder to cure. Let me try to explain. The germs that cause TB, like you and me, are living things. And like all living things they don’t want to be killed. Sometimes TB germs can start to understand how the medicines usually used against them work. This happens when someone with TB misses times when they should take tablets as the TB doctor or nurse told them to. When someone with TB misses their tablets it creates gaps when the TB germs have extra time to understand and learn how the tablets work. When TB germs know how the medicines work it can avoid being killed by them, so they stay alive and continue to reproduce making a person with TB sick again. When the TB germs understand how the medicines work and stop working as well as they usually should, then this is called multidrug-resistant TB or MDR-TB.

MDR-TB happens in one of two ways. The first is that you can come into contact with someone who already has MDR-TB and is infectious and you breathe in the already drug-resistant TB germs. The second is that someone may start off with common TB, but does not take all of their

TB medicines properly. Then the germ “learns” how the drugs work and the TB “changes” from being standard or common TB and becomes MDR-TB. If you have MDR-TB and you still continue

to not take your medication properly, the TB germs learn even more until the TB medicines won’t work very well, if at all. When this happens it is very serious and called extensively drug-resistant TB or XDR-TB.

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Extensively drug-resistant TB (XDR-TB) is even more serious than MDR-TB. I described a process above whereby the TB germ can learn how the TB medicine usually used against it works. When this happens the TB germ becomes resistant to treatment. When the TB germ recognizes the main preferred medicine used to cure the disease this is called MDR-TB. If the patient with MDR-TB continues to not take their TB medication as their TB doctor or nurse tells them to, then there is a chance that the severity of the resistance shall increase. When MDR-TB becomes even more resistant to the special medicine, called “second-line” TB treatment, then the options for cure start to become more limited. This is because there is a lack of drugs that can cure this form of TB. This is called XDR-TB.

It is not known how common XDR-TB is, only to say that it is rare. However, the increasing identification of XDR-TB in some parts of the world is very worrying. MDR-TB and XDR-TB are both transmitted in the same way as common TB. It means that anyone can be infected and they may go on to develop active disease. If someone is found to have XDR-TB, it is quite possible that they shall be isolated at home or in hospital to prevent passing on the drug-resistant germ to anyone else (See Chapter four on Isolation). The best way to avoid any chance of MDR-TB, or XDR-TB developing is to ensure that you take your TB tablets as your TB doctor or nurse tells you to and only stop when they say you can. Drug-resistance can be prevented. It s best not to let it happen in the first place.

XDR-TB can be extremely difficult or in some cases virtually impossible to cure.

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In some parts of the world there are many people living with HIV. When someone is HIV-positive the chances that they may develop active TB disease increases. Large numbers of the world’s population, as mentioned earlier, are latently infected with TB. As I have made clear, it’s very common and doesn’t mean that a person is infectious and can pass the disease onto others. In other words, although the TB germs are present in the body, the disease does not develop, remaining asleep (like a volcano that is dormant and probably won’t ever erupt, so to speak). This is because when our body is healthy, its defence mechanism stops the TB germs from multiplying. However, if for any reason the body’s defence mechanism is weakened (for example by having HIV), the germs are no longer controlled and can wake up, then the latently infected person can become sick with active TB disease.

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