Flash is required to view this map

Tuberculosis

Tuberculosis is an infection caused by the bacteria mycobacterium tuberculosis that can vary in presentation from no initial symptoms in the majority of individuals, to a rapidly progressive infection that can involve nearly every organ system in immunodeficient individuals (HIV) or infants. The infection is most common in poor and developing countries, but occur world wide.

It is spread by breathing air containing mycobacterium tuberculosis; produced when individuals with respiratory (laryngeal) or lung infection cough, sneeze or sing. It is generally felt that one needs close contact with the air of an infected person to become infected; being in the same room, household, an enclosed space like airplane cabin etc.

The initial infection does not produce symptoms in the vast majority; as the immune system contains the mycobacterium and is only recognized by doing a TB skin test (PPD) which can show reactivity (an area of swelling and or redness at the site of injection) within 3 weeks to 2 months after exposure.

Nearly 90% of immunocompetent adults, who have tuberculosis infection manifested solely by a positive skin test, will never develop active disease. The lifetime risk of developing active tuberculosis in adults with an intact immune system, whose skin test becomes positive after an exposure, is 10%, and half of them will develop active disease in the first two years.

Individuals who have recently become infected (+ PPD test) can dramatically reduce that 10% risk of developing active disease by taking prophylactic antibiotics (isoniazid, rifampin etc). Prophylactic therapy reduces the risk of developing active disease by nearly ninety percent.

Active disease develops when the immune system is no longer able to control the mycobacterium and it starts multiplying and destroying tissues. Active disease commonly manifests as lung infection but can involve any organ system like lymph nodes, pericardium, kidneys, bones and joints, skin gastrointestinal system and central nervous system.

Where does it occur?

It occurs worldwide, but incidence is higher in cities and developing countries.

How is it transmitted?

It is transmitted primarily by inhaling air containing mycobacterium tuberculosis (tubercle bacilli). Infected individuals can release the tubercle bacilli through coughing, sneezing, talking and singing. Healthcare workers may become exposed through activities of intubation, autopsy, bronchoscopy or rarely dressing changes of tuberculosis abscesses. Direct entry of the bacteria through cuts or breaks in the skin is also possible but rare.

It is generally felt that one needs close contact with the air of an infected person to become infected; being in the same room, household, an enclosed space like airplane cabin etc. Outbreaks are usually associated with crowded and closed environments like prisons, hospitals, homeless shelters, nursing homes and schools.

One probably does not contract the infection from open air outdoor settings. It is not felt to be contagious from surfaces like countertops etc.

Is it contagious from person to person?

It is contagious from person to person, and remains so for at least 4-8 weeks into treatment, depending on the severity of infection. One can only definitely say that the infected person is not contagious once the sputum specimens no longer grow the bacteria in culture media, which will take 6 weeks to demonstrate. If the infected person’s sputum does not demonstrates the bacteria under the microscope they are probably at minimal risk of being contagious. Please check with the local health department for local regulations.

What is the risk for travelers?

The risk is generally low unless living or working in crowded conditions in developing countries.

How soon after exposure will one develop symptoms?

Most people do not have symptoms and can only be diagnosed as having infection by doing a skin test (PPD), which will become reactive (swelling with or without associated redness) in 2 weeks to 2 months after exposure.

Outward symptoms of active disease commonly develop within 2 years of exposure, but there is a life time risk of developing disease.

What are the signs and symptoms?

The symptoms of active tuberculosis depend on the organ system involved in the disease.

With lung involvement one sees cough productive of yellow to bloody phlegm, chest pain, fever, chills, sweats and weight loss.

Central nervous system infection causes meningitis and produces symptoms of fever, headache, stiff neck, nausea, vomiting or focal weakness; symptoms tend to develop over weeks as opposed to bacterial meningitis that develop over days.

Bone and joint infection commonly involves the spine and is manifested by back pain, stiffness and tenderness over the involved spine. If the infection spreads to adjoining muscles or the spinal cord one can see weakness and paralysis. Large joints of the hips and knees, ankles, elbows etc can be involved with pain and swelling.

Genitourinary system infection can cause flank pain, burning with urination, frequent urination, swelling of testicles etc.

Gastrointestinal system infection can cause ulcers from the mouth to anus, abdominal pain, nausea and vomiting with obstruction of bowels and perforation with bleeding. Seeding of the abdominal wall lining (peritoneum) can result in fluid building up in the abdomen (ascites) with swelling and pain.

Infection of the skin and lymph glands can result in draining swollen ulcers and lymph glands.

Are there any lab tests to diagnose the illness?

The tuberculin skin test (PPD) is used to diagnose infection, the subcutaneous skin is injected with a special protein derivative and skin reaction is measured in 48 hours for signs of swelling. A swelling that measures from 5 mm to 15 mm is considered positive depending on your immune status, timing of exposure and other risk factors. Please consult your physician for specific situations.

With active disease the bacteria can be seen under the microscope or grown on culture media from sputum or other infected body fluids. PCR tests are available as well to diagnose the illness.

Is there any treatment?

Antibiotics like isoniazid, rifampin, ethambutol, pyrazinamide etc, along with vitamin b6, in combination, for a prolonged length of time are effective in treating the infection. For difficult cases or with resistant strains other antibiotics and surgery may be required.

What preventive measures can be taken?

Wear protective masks if coming in contact with actively infected individuals.

Avoid staying in overcrowded places while traveling.

BCG vaccine is only effective in preventing disseminated or central nervous system involvement in individuals less than 5 years of age and is not recommended in western countries.

If you develop a positive skin test, consult your physician to see if taking prophylactic antibiotics would be indicated and beneficial in your situation.

advice for your illness and travel
learn about an exotic disease