Differentials
Legionella infection
SIGNS / SYMPTOMS
Known contact with Legionella.
INVESTIGATIONS
Urine antigen test for Legionella: positive.
Tularaemia
SIGNS / SYMPTOMS
Localised unilateral lymphadenopathy, painful skin ulcer, or unilateral conjunctivitis.
INVESTIGATIONS
Blood cultures and cultures from respiratory secretions: positive for Francisella tularensis.
Viral hepatitis
SIGNS / SYMPTOMS
Gastrointestinal symptoms and jaundice.
Risk factors for exposure.
INVESTIGATIONS
Viral hepatitis serologies (mostly hepatitis A, B, and C): positive.
Influenza infection
SIGNS / SYMPTOMS
No differentiating features.
INVESTIGATIONS
Rapid antigen test, polymerase chain reaction, or cultures from respiratory secretions: may be positive for influenza virus.
Mycoplasma infection
SIGNS / SYMPTOMS
No differentiating features.
INVESTIGATIONS
Polymerase chain reaction or serology: positive for Mycoplasma species.
Rickettsial disease
SIGNS / SYMPTOMS
Patients may present with hepatosplenomegaly.[81]
History reveals recent exposure/bite from lice, mites, fleas, or ticks.
INVESTIGATIONS
Polymerase chain reaction or serology: positive for Rickettsia species.
Sandfly fever
SIGNS / SYMPTOMS
Patients may present with conjunctival suffusion.[81]
History reveals recent exposure/bite from sandflies.
INVESTIGATIONS
Polymerase chain reaction or serology: positive for Phlebovirus.
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