Prevention of opportunistic infections in HIV

Pneumocystis jirovecii pneumonia is a subacute, often hypoxic pneumonia in patients with CD4 counts below 200/mcL or comparable immunosuppression, diagnosed by organism visualization on induced sputum or bronchoalveolar lavage and treated with 21 days of high-dose trimethoprim-sulfamethoxazole plus adjunctive steroids when hypoxic.

Toxoplasmosis is infection with the protozoan Toxoplasma gondii, acquired from undercooked meat or cat feces, causing a mononucleosis-like illness in immunocompetent hosts, reactivation encephalitis with ring-enhancing brain lesions in advanced HIV, and a severe congenital syndrome after maternal primary infection in pregnancy. Diagnosis in CNS disease is largely presumptive on serology, imaging, and empiric treatment response, and management is pyrimethamine-sulfadiazine-leucovorin, with prevention centered on CD4-based prophylaxis and food/cat-litter precautions in pregnancy.

Histoplasma capsulatum is an endemic dimorphic fungus, acquired by inhalation of conidia in the Mississippi and Ohio River valleys and other endemic regions, that most often causes asymptomatic or mild pulmonary infection but can disseminate in immunosuppressed hosts; diagnosis rests on the Histoplasma urinary antigen assay and treatment is itraconazole for mild to moderate disease or liposomal amphotericin B followed by itraconazole for severe or disseminated infection.

Coccidioidomycosis, or valley fever, is a dimorphic fungal infection acquired by inhaling Coccidioides arthroconidia in the southwestern United States, ranging from self-limited pneumonia to disseminated or meningeal disease, diagnosed by culture, histopathology, or serology and treated with fluconazole for symptomatic disease and lifelong fluconazole for meningitis.

Cytomegalovirus is a ubiquitous herpesvirus that is usually asymptomatic or causes a heterophile-negative mononucleosis-like illness in healthy hosts, but reactivates to cause retinitis, colitis, pneumonitis, or encephalitis in transplant recipients and patients with AIDS; treatment is systemic ganciclovir or valganciclovir, with foscarnet and cidofovir reserved for resistance or intolerance.

Cryptococcal meningoencephalitis is the most common cause of fungal meningitis worldwide, driven by CNS dissemination of inhaled Cryptococcus in an immunosuppressed host, typically HIV with a CD4 count under 50; treatment is induction amphotericin B plus flucytosine, consolidation and maintenance fluconazole, and aggressive lowering of elevated intracranial pressure.

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.

Antiretroviral therapy (ART) combines three or more drugs from at least two classes to suppress HIV replication. First-line therapy is bictegravir/emtricitabine/tenofovir alafenamide or dolutegravir-based triple therapy, started as soon as the patient is ready regardless of CD4 count, and continued for life to prevent AIDS and transmission.

Acute HIV infection, also called the acute retroviral syndrome, is the symptomatic viremic phase in the days to weeks after HIV acquisition, presenting with fever, fatigue, myalgia, rash, and pharyngitis at a time when antibody testing may still be negative. Diagnosis requires an HIV RNA viral load, and antiretroviral therapy should begin as soon as the patient is ready, regardless of CD4 count.

Vaccines are live attenuated, inactivated, subunit, conjugate, or toxoid preparations that induce antigen-specific active immunity to prevent infection or its complications before exposure occurs. Selection follows the age- and risk-based Advisory Committee on Immunization Practices schedule, with routine adult boosting such as Tdap every 10 years, and inactivated regimens substituted whenever a live vaccine is contraindicated by pregnancy or immunosuppression.

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.

Meningococcal meningitis is an acute bacterial infection of the meninges caused by Neisseria meningitidis, an encapsulated gram-negative diplococcus that spreads by respiratory droplets and classically causes a petechial rash. It is an infectious disease emergency treated with empiric ceftriaxone and vancomycin plus dexamethasone, followed by penicillin or ceftriaxone once confirmed, with chemoprophylaxis for close contacts.