PREVALENCE OF TUBERCULOSIS
Tuberculosis (TB) is caused by Mycobacterium tuberculosis, which usually attacks the lungs. This bacteria is most commonly spread when someone with active TB disease expels the bacteria in airborne droplets by coughing, sneezing, speaking, singing, etc.
TB is one of the most deadly diseases in the world today, killing nearly 1.5 million people annually, mostly in developing countries and lower- and middle-income settings. About one third of the world population has latent TB (WHO, 2016). At least 9 million people become newly infected with TB every year, and an estimated 3 million new cases each year go undetected, causing further transmission. In the United States, it was at one time the leading cause of death, but TB mortality has decreased in recent decades (Keshavjee et al., 2015).
Vaccination and Drug Treatment
In 1921 in France, the first TB vaccine was administered to humans. In 1943, the first antibiotic treatment was developed for the disease, called streptomycin. (This drug is no longer a first-line treatment for tuberculosis.) But drug-resistant strains of TB emerged almost immediately after the introduction of streptomycin, and a rapid succession of other anti-TB drugs appeared in the following years. Antibiotics continue as the treatment for tuberculosis, most commonly used in combination to reduce the risk of developing resistance (Schoenstadt, 2008).
People who are infected but do not have TB disease are asymptomatic and not infectious; they usually have a positive reaction to the tuberculin skin test. Many people who have latent TB infection (LTBI) never develop active TB disease, although this group serves as the largest reservoir for those who may develop the disease. As many as 2 billion people worldwide may have LTBI. In people who have weak immune systems, the bacteria become active and cause TB disease. Although the majority of TB cases are pulmonary, TB can occur in almost any anatomical site or as a disseminated disease (Turetz & Ma, 2016).
Trends in the United States
Despite their drastic decrease throughout the twentieth century, in the late 1980s, TB cases started increasing again and peaked in 1992. This was attributed to several factors:
- The onset of the HIV epidemic and its related immunosuppression
- Increases in immigration of persons from countries where TB disease was common
- TB transmission in congregate settings (e.g., correctional facilities, long-term care facilities, homeless shelters)
- The development of multidrug-resistant TB (MDR-TB)(CDC, 2015)
At least 9 million people become newly infected with TB every year, and an estimated 3 million new cases each year go undetected, causing further transmission.
TRANSMISSION
Mycobacterium tuberculosis is spread from person to person through the air. When a person with pulmonary or laryngeal TB coughs, sneezes, speaks, or sings, droplet nuclei containing tubercle bacilli (M. tuberculosis organisms) are expelled into the air. Depending on the environment, larger droplets will fall almost immediately to the ground, while tiny particles can remain suspended in the air for longer periods of time (Yates et al., 2016).
When a susceptible individual inhales droplet nuclei containing the tubercle bacilli, TB transmission may occur. The primary factors that affect the probability that TB will be transmitted include the:
- Number of tubercle bacilli an individual expels into the air
- Severity of infectiousness of the individual with TB disease
- Environment in which exposure occurred
- Duration of exposure
- Virulence of the organisms
- Immune system of the recipient (Yates et al., 2016)
In the hospital, the best way to stop the transmission of suspected or confirmed infectious TB disease is to place the patient in a private room with Airborne Precautions instituted and then immediately begin effective TB therapy. Infectiousness declines rapidly after adequate standardized therapy is started, as long as the patient adheres to the prescribed regimen (Yates et al., 2016).
DIAGNOSIS
Presentation
The signs and symptoms of pulmonary TB may include the following:
- Cough (duration of >3 weeks)
- Chest pain
- Hemoptysis (expectoration of blood or of blood-stained sputum)
- Weakness or fatigue
- Fever
- Chills
- Weight loss
- Radiography showing TB(Campos et al., 2016)
The symptoms may be mild or overlooked for months. This may result in delays seeking healthcare and cause transmission of the infection to others. An actively infected person may transmit the disease to as many as 10 to 15 persons in a year (WHO, 2013).
Symptoms of extrapulmonary TB depend on the site affected. Tuberculosis of the spine may cause pain in the back; TB of the kidney may cause blood in the urine. Extrapulmonary TB should be considered in the differential diagnosis of ill individuals who have systemic symptoms and are at high risk for TB (CDC, 2013b).
Medical History
It is important to ask individuals suspected of having TB about their history of TB exposure, infection, or disease. Clinicians may also contact the local health department for information about whether a patient has received TB treatment in the past. If the treatment regimen was inadequate, or if the patient did not adhere to therapy, TB may recur and may be drug-resistant.
It is also important to consider demographic factors (country of origin, age, gender, ethnic or racial group, occupation) that may increase the patient’s risk for exposure to TB or to drug-resistant TB disease. In addition, clinicians should determine whether the patient has medical conditions, especially HIV infection, that increase the risk for latent TB infection to progress to TB disease. Patients who do not know their current HIV status are referred for HIV counseling and testing.
Physical Exam
A physical examination is an essential part of the evaluation of any patient. It cannot be used to confirm or rule out TB, but it can provide valuable information about the patient’s overall condition and other factors that may affect how TB is treated.
Certain manifestations of tuberculosis, such as erythema nodosum, can be diagnosed on the basis of physical examination alone since the cutaneous nodules that extend to the layer of subcutaneous tissue are very distinctive (Bataduwaarachchi & Tissera, 2015).
A physical examination may reveal symptoms of tuberculosis, including persistent cough, hemoptysis, fever, chills, or adventitious breath sounds. In the absence of a physical examination, a patient’s tuberculosis symptoms may be subclinical and go unrecognized for a long time (WHO, 2013).
TB Testing
Targeted testing for TB infection is done to identify individuals who are at high risk of developing TB disease and who would benefit from treatment. All testing activities should be accompanied by a plan for follow-up medical evaluation and treatment for individuals with TB infection or TB disease. Individuals with a positive test for TB infection should be evaluated for TB disease and, if disease is ruled out, considered for treatment for LTBI (CDC, 2013a).
In the United States, the two preferred methods for detecting TB infection are the Mantoux tuberculin skin test (TST) and the QuantiFERON-TB Gold test (QFT-G). The latter replaced the original QuantiFERON-TB test (QFT) (CDC, 2013a).
Special testing situations include those involving pregnant women, live virus vaccination, anergy, boosted reaction, two-step testing, and occupational settings.
It is the responsibility of the primary healthcare provider to promptly report all suspected or confirmed cases of TB to the state or local health department so that a contact investigation can be initiated quickly to interrupt the potential ongoing transmission. Each jurisdiction maintains its own policies for conveying this information.
TREATMENT OF TB DISEASE
Tuberculosis disease must be treated over a long period of time compared to many other infectious diseases. If treatment is not continued for a sufficient length of time, some tubercle bacilli may survive and the patient may become ill and infectious again.
The principles for the treatment of tuberculosis are to:
- Cure the patient and restore health, quality of life, and productivity
- Prevent death from active TB or its complications
- Prevent relapse of TB
- Reduce transmission of TB to others, especially those closest to the patient
- Prevent the development of acquired drug resistance (DOH RSA, 2014)
For each patient with newly diagnosed TB, a specific treatment and monitoring plan should be developed. This plan includes immediate initiation of combination drug therapy and should include a description of the treatment regimen, the methods of assessing and ensuring adherence to the antituberculosis regimen, and the methods of monitoring for adverse reactions. Health teaching may include nutritional counseling, smoking cessation, Alcoholics or Narcotics Anonymous (if needed), and at least one year of follow up medical care (Ignatavicius & Workman, 2015).
Treatment Regimens
Tuberculosis treatment regimens must contain multiple drugs to which the organisms are susceptible. Treatment with a single drug can lead to the development of a bacterial population resistant to that drug. Likewise, the addition of a single drug to a failing antituberculosis regimen can lead to drug resistance (Zumla et al., 2013).
As of 2016, there are 10 drugs approved by the U.S. Food and Drug Administration for treating TB. Of the approved drugs, isoniazid (INH), rifampin (Rifadin), ethambutol (Myambutol), and pyrazinamide (PZA) are considered first-line antituberculosis agents, forming the core of initial treatment regimens (CDC, 2016).
Patient Monitoring
Clinicians who treat TB must be familiar with the methods of monitoring for adverse reactions and treatment responses among patients. All patients need to be monitored to assess their response to therapy and compliance. In some situations (drug-resistant TB, pregnancy, HIV-positive patients), expert consultation may be required.
Patients need clinical evaluations at least monthly to identify possible adverse reactions to medications and to assess adherence. A patient’s weight is monitored monthly, and dosages are adjusted according to weight changes. Patients who have stable abnormalities of hepatic or renal function at baseline need repeat measurements early in the course of their treatment, then less frequently, to ensure the damage has not worsened.
Patient Education
When educating patients, topics include:
- What medication should be taken, how much, how often, and when
- Possible adverse reactions to the medications
- When to seek necessary medical attention
- Consequences of not taking medicine correctly
- TB infection control measures and potential need for isolation (CDC, 2013b)
Healthcare providers must take the time to clearly explain to patients when, how much, and how often the treatment medication needs to be taken, especially if the patient is not receiving directly observed therapy (DOT). Written instructions are also provided. Additionally, all patients with TB are advised to undergo voluntary counseling and testing for HIV infection.
INFECTION PREVENTION AND CONTROL
Healthcare Setting
In the healthcare setting, transmission of the bacteria is prevented by the use of a specially designed patient room and personal protective equipment. An airborne infection isolation (AII) room contains negative pressure that prevents the air from leaving the room where it is filtered via a high-efficiency particulate air (HEPA) filter to prevent adjacent areas from becoming contaminated. Hospital personnel and visitors are required to wear gloves, gowns, and masks when in contact with the patient. Particulate respirator masks are required for healthcare personnel caring for a TB positive patient that require annual fit testing to ensure efficacy. The patient must be masked when transported within the hospital for procedures.
Local Health Department Role
State and local health departments have the primary responsibility for preventing and controlling TB. However, those who provide TB services in settings such as private clinics, managed care organizations, HIV clinics, homeless shelters, long-term care facilities, emergency medical services, correctional facilities, and hospitals also have responsibility for preventing and controlling TB in their communities (CDC, 2013b). It is crucial that local health departments coordinate care with other healthcare providers and facilities in the following areas:
- Overall planning and policy development
- Identification of individuals who have clinically active TB
- Maintaining a registry of all TB patients
- Management of individuals who have disease or who are suspected of having disease
- Finding and evaluating those who have been in contact with individuals infected with M. tuberculosis
- Identification and management of individuals infected with M. tuberculosis
- Data collection and analysis, including reporting to the CDC
- Legal authority to detain TB patients for examination, isolation, or treatment to protect the public’s health
- Training and education (County of Los Angeles Public Health, 2016)
In the United States, it is the responsibility of the public health department to identify, interview, and test the contacts of people positive for TB. The CDC recommends that a TB-positive patient be interviewed within one day of laboratory results being reported to the health department. Public health nurses should visit possible exposure sites within three days of the interview, with possible contacts tested within three working days after that. Without treatment, about 5% to 10% of infected persons will develop TB disease (CDC, 2014).
TB Reporting Requirements
Early detection of tuberculosis is essential to ensure initiation of appropriate treatment and to identify contacts that may also be infected with TB. The CDC recommends clinicians report positive cases of TB to the nearest health department within two days of identification. Laboratories should report positive test results to the healthcare provider who ordered the test within one day. However, reporting requirements are specific to the county or municipality in which the local health department is located (County of Los Angeles Public Health, 2016).
CONCLUSION
There has been a drastic reduction in the number of TB cases in the United States, with TB now affecting primarily the elderly and immunocompromised. In the rest of the world, TB is much more prevalent, with the World Health Organization estimating that approximately one third of the world population is positive for the TB bacteria. In 2016 the WHO announced an “End TB Strategy,” with plans to eliminate TB globally by 2030.
In the United States, local public health departments carry the responsibility for taking reports of suspected and verified cases of TB from healthcare personnel and laboratories. The health departments then evaluate patient environments and contacts to identify other possible sources of infection. Creating treatment regimes, monitoring drug susceptibility and treatment outcomes, conducting directly observed therapy (DOT), and promoting community education are also in the purview of local health departments.
In the hospital setting, institutions carry administrative responsibility to identify, treat, and prevent the transmission of TB. Diagnosis of TB is usually made by a review of the symptoms; history, including risk factors; and skin, sputum, or blood testing. The two most common forms of testing in the United States are the Mantoux tuberculin skin test (TST) and the Quantiferon-TB Gold blood test (QTB-G). Other tests are used but not considered as definitive.
Treatment of TB consists of a combination of drugs, such as isoniazid and rifampin, usually for six to nine months. Recent research indicates that a much lower number of doses (12) over a period of three months is available but not effective for all patients. Some patients must be observed taking their medications to ensure compliance in a DOT regime.
REFERENCES
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Campos LC, Rocha MV, Willers DM, & Silva DR. (2016). Characteristics of patients with smear-negative pulmonary tuberculosis (TB) in a region with high TB and HIV prevalence. PLoS One, 11(1). doi:http://dx.doi.org/10.1371/journal.pone.0147933
Centers for Disease Control and Prevention (CDC). (2016). Treatment for TB disease. Retrieved from http://www.cdc.gov/tb/topic/treatment/tbdisease.htm
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