Saturday, February 29, 2020

Airborne infectious disease

Airborne infectious disease Tuberculosis (TB) is an airborne infectious disease which is caused by bacteria belonging to Mycobacterium tuberculosis complex1. There are approximately one third of the world’s population are infected with tuberculosis where nine millions of new cases reported annually2. Although tuberculosis is essentially curable and preventable, it continues to cause millions of deaths every year2. When infected individual coughs, sneezes or spits, M. tuberculosis is propelled into the air and infected those who breathed in the bacteria that existed in droplets of saliva3. Primarily, tuberculosis will affect the lungs, known as pulmonary tuberculosis3. It will also affect other parts of body, for instance lymph nodes, bones, brain and kidneys3. Once a person is infected with tuberculosis, there are basically three possible ways may occur. Firstly, the immune system plays a vital role and strong enough to kill the bacteria3. Secondly, immune system is not strong enough to fight off the ba cteria but is able to build a defensive barrier against the bacteria3. Individuals who are latently infected with M. tuberculosis show asymptomatic where these bacteria lie dormant in the lungs and able to reactivate after years1. The disease is often reactivated in those who are immunocompromised or generally weakened. Lastly, the immune system fails to kill bacteria causing the bacteria to grow and spread towards other parts of body which is called active tuberculosis3. In the fight of tuberculosis, World Health Organisation (WHO) recommends universal Bacille Calmette-Guà ©rin (BCG) vaccination in the countries with high TB burdens4. BCG vaccine contains weakened form of M. tuberculosiswhich will induce antibodies to fight against this type of bacteria. The efficacy of BCG vaccination can be ranging from 0% to 84%5. This may be due to the frequency of TB exposure and quality of vaccine used, leading to arguments on BCG vaccination efficacies4. One of the greatest arguments is th at BCG vaccination causing positive reactions to tuberculin skin testing and hence interfere with the diagnosis of latent TB4. Existence of evidences showing the rates of efficacy also depends on geographical location, age at vaccination and form of TB further complicate the situation. Currently, TB chemotherapy is made up of a cocktail of first-line drugs isoniazid (INH), rifampicin (RIF), pyrazinamide (PZA) and ethambutol (EMB) 6. If the treatment fails due to bacterial drug resistance, or patient unable to tolerate, second-line drugs for instance para-aminosalicylate (PAS), fluoroquinolones, ethionamide and cycloserine are introduced6. These are considered as second line drugs generally either less potent with larger doses or more toxic with serious side effects6. Tuberculosis is presently treated in two phases, namely initial phase and continuous phase7. In initial phase, the patient will be treated with concurrent use of four first line drugs, with the aim to eradicate or contr ol bacteria population to replicate in rapid motion and also avoid the emergence of bacteria resistance7. The treatment choices available for initial treatment include isoniazid, rifampicin, pyrazinamide and ethambutol7. Streptomycin is used rarely but can be used in patients who infected with bacteria that are resistant to isoniazid before the therapy is commenced7. The duration for initial phase is 2 months whereas the continuous phase takes 4 months7. During the four months of continuous phase, patients are treated with isoniazid and rifampicin at same doses7. Most of the TB treatment is supervised where drug administration needs to be fully supervised by healthcare professions since lengthy duration of treatment causing incompliance in patients7. These patients who are unlikely to be compliance will be given the drugs three times a week until the course is completed while patients who able to comply with the treatment will not be supervised7.

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