Isolation precautions

Tuberculosis, caused by Mycobacterium tuberculosis, remains a leading global cause of infectious death and presents as latent infection, primary/secondary pulmonary disease, or extrapulmonary and disseminated (miliary) disease. Diagnosis rests on AFB smear, NAAT, and mycobacterial culture (the gold standard), and drug-susceptible active disease is treated with a four-drug regimen (isoniazid, rifampin, pyrazinamide, ethambutol) for 2 months followed by isoniazid plus rifampin for 4 to 7 months.

Measles (rubeola) is a highly contagious paramyxovirus infection that has re-emerged in the United States because of low vaccination rates, presenting with a prodrome of the 4 C's followed by a cephalocaudal maculopapular rash, confirmed by PCR or IgM, and managed with supportive care plus vitamin A.

Whooping cough is a highly infectious bronchitis caused by the gram-negative coccobacillus Bordetella pertussis, marked by catarrhal, paroxysmal, and convalescent stages with lymphocytosis; diagnosis is clinical, confirmed by nasopharyngeal PCR, and treated with azithromycin plus prophylaxis of close contacts.

Herpes zoster is reactivation of latent varicella-zoster virus from a sensory ganglion, producing a painful, dermatomal vesicular rash that does not cross the midline, most common in adults older than 60 years and in immunosuppressed hosts; diagnosis is clinical, confirmed by VZV PCR when needed, and antiviral therapy started within 72 hours of rash onset shortens the illness and reduces postherpetic neuralgia.

Clostridioides difficile infection is toxin-mediated colitis that follows disruption of normal colonic flora, most often by antibiotics, and ranges from watery diarrhea to fulminant colitis with shock, ileus, or megacolon. Diagnosis rests on unformed stool testing (NAAT and/or toxin EIA) in a patient with three or more unformed stools in 24 hours, and treatment is chosen by IDSA/SHEA severity grade, oral vancomycin or fidaxomicin for 10 days, escalating to high-dose vancomycin plus IV metronidazole for fulminant disease.

Sepsis is life-threatening organ dysfunction caused by a dysregulated host response to infection, identified by an acute rise in SOFA score of 2 points or more in a patient with known or suspected infection. Survival depends on recognizing the pattern early and completing the hour-1 bundle: lactate, blood cultures before antibiotics, broad-spectrum antibiotics such as cefepime 2 g IV every 8 hours, and 30 mL/kg crystalloid for hypotension or a lactate of 4 mmol/L or higher.

Plague is infection with the gram-negative coccobacillus Yersinia pestis, transmitted by rodent fleas, presenting as bubonic, septicemic, or pneumonic disease with sudden fever and, in the bubonic form, an intensely painful regional bubo. Diagnosis rests on Gram/Wright-Giemsa stain and culture of aspirate, blood, or sputum, and treatment is empiric streptomycin or gentamicin, or a fluoroquinolone, started without waiting for confirmation because untreated pneumonic plague is uniformly fatal.

Ebola virus disease is a filoviral hemorrhagic fever spread by direct contact with infected body fluids that progresses from a nonspecific febrile illness to diffuse hemorrhage, shock, and multiorgan failure with mortality that can reach 90 percent, and is treated with immediate isolation, supportive care, and a Zaire ebolavirus-specific monoclonal antibody.