West Nile virus infection

Herpes simplex virus type 1 or 2 establishes lifelong latency in sensory ganglia after mucocutaneous infection, causing painful vesicular-to-ulcerative outbreaks of the mouth or genitals with intermittent asymptomatic shedding; diagnosis is by NAAT of an ulcer swab and treatment is oral nucleoside analogues, escalating to intravenous acyclovir for encephalitis, severe mucocutaneous disease, or disseminated infection in immunosuppressed hosts.

Lyme disease is a tick-borne spirochetal infection caused by Borrelia burgdorferi that progresses from erythema migrans through early disseminated cardiac and neurologic disease to late arthritis, diagnosed clinically when erythema migrans is present and otherwise by two-tiered serology, and treated with staged doxycycline, amoxicillin, or cefuroxime regimens.

Acute purulent infection of the meninges beyond the neonatal period, most often from Streptococcus pneumoniae or Neisseria meningitidis, diagnosed by CSF analysis after prompt lumbar puncture and treated with immediate empiric intravenous antibiotics plus adjunctive dexamethasone, since any delay in therapy worsens outcome and mortality remains near 25%.

Poliomyelitis is caused by poliovirus, a fecal-orally transmitted picornavirus that destroys anterior horn motor neurons after hematogenous spread from the gut, producing asymmetric lower motor neuron flaccid paralysis in under 1% of infected people. Diagnosis rests on the clinical picture supported by cerebrospinal fluid lymphocytic pleocytosis and isolation of the virus from stool or throat secretions, treatment is supportive with ventilatory support for respiratory muscle involvement, and prevention is universal inactivated poliovirus vaccination in childhood.

Japanese encephalitis is a mosquito-borne flavivirus infection and the leading vaccine-preventable cause of viral encephalitis in Asia, confirmed by cerebrospinal fluid IgM antibody testing and managed with supportive care plus empiric acyclovir until herpes simplex encephalitis is excluded.

Dengue is a flavivirus spread by daytime-feeding Aedes mosquitoes that causes an acute febrile illness with retro-orbital pain and severe myalgia, and can progress to hemorrhagic fever and shock, especially on heterotypic secondary infection; management is supportive with acetaminophen and fluids, avoiding NSAIDs and aspirin.

Zika virus is an Aedes-transmitted flavivirus causing a usually mild febrile illness with rash and conjunctivitis, but infection during pregnancy can cross the placenta and cause congenital Zika syndrome with microcephaly, and postinfectious Guillain-Barre syndrome is a recognized complication. Diagnosis uses RT-PCR in the first 2 weeks of illness and IgM serology thereafter, treatment is supportive, and prevention centers on avoiding travel to endemic areas during pregnancy and preventing sexual transmission.

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.