Re: Local Mice Test Positive For Hantavirus
FROM THE MERCK MEDICAL MANUAL:
Hantavirus Infection
The genus Hantavirus consists of at least 4 serogroups with 9 viruses causing 2 major, sometimes overlapping, clinical syndromes: hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS). Viruses causing HFRS are Hantaan, Seoul, Dobrava (Belgrade), and Puumala. Those causing HPS are Sin Nombre, Black Creek Canal, Bayou, and New York-1. Hantaviruses occur in wild rodents throughout the world, who shed it throughout life in urine and feces. Transmission occurs between rodents. Transmission to humans is through inhalation of aerosols of rodent excreta. Recent evidence suggests human-to-human transmission may occur on rare occasions. Naturally and laboratory-acquired infections are becoming more common.
Laboratory diagnosis of Hantavirus infection is established by serologic tests and reverse transcriptase?PCR (rt-PCR). Serologic tests include enzyme-linked immunosorbent assay (ELISA) and Western and strip immunoblot assays. Growth of the virus is technically difficult and requires a biosafety level 3 laboratory.
Hemorrhagic Fever With Renal Syndrome (HFRS)
(Epidemic Nephrosonephritis; Korean Hemorrhagic Fever; Nephropathia Epidemica)
Hemorrhagic fever with renal syndrome begins as a flu-like illness and may progress to shock, bleeding, and renal failure. Diagnosis is with serologic tests and PCR. Mortality is 6 to 15%. Treatment includes IV ribavirin.
Some forms of hemorrhagic fever with renal syndrome (HFRS) are mild (eg, nephropathia epidemica, caused by Puumala virus, occurring in Scandinavia, the western part of the former Soviet Union, and Europe), while others are severe (eg, those caused by Hantaan, Seoul, and Dobrava viruses as occur in Korea or the Balkans).
Symptoms, Signs, and Diagnosis
Incubation is about 2 wk. In mild forms, infection is often asymptomatic. When symptoms occur, onset is sudden, with high fever, headache, backache, and abdominal pain. On the 3rd or 4th day, subconjunctival hemorrhages, palatal petechiae, and a truncal petechial rash may appear. Diffuse reddening of the face that resembles sunburn, with dermatographism, occurs in > 90%. Relative bradycardia is present, and transient mild hypotension occurs in about 1⁄2 with shock in a minority. After the 4th day, renal failure develops. About 20% of patients become mentally obtunded. Seizures or severe focal neurologic symptoms occur in 1%. The rash subsides; the patient develops polyuria and recovers over several weeks. Proteinuria, hematuria, and pyuria may develop.
HFRS is suspected in patients with possible exposure who have fever, a bleeding tendency, and renal failure. If suspected, CBC, electrolytes, renal function tests, coagulation tests, and urinalysis are obtained. During the hypotensive phase, the Hct increases and leukocytosis and thrombocytopenia develop. Albuminuria, hematuria, RBC and WBC casts may develop, usually between the 2nd and 5th day. During the diuretic phase, electrolyte abnormalities are common. Diagnosis of HFRS is ultimately based on serology or PCR.
Prognosis and Treatment
Death can occur during the diuretic phase secondary to volume depletion, electrolyte disturbances, and secondary infections. Recovery usually takes 3 to 6 wk but may take up to 6 mo. Overall mortality is 6 to 15%, almost all of which occurs in the more severe forms. Residual renal dysfunction is uncommon except with severe disease that occurs in the Balkans.
Treatment is with IV ribavirin
Some Trade Names
VIRAZOLE
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(loading dose 30 mg/kg, then 16 mg/kg q 6 h for 4 days, then 8 mg/kg q 8 h for 3 days). Supportive care, which may include renal dialysis, is critical, particularly during the diuretic phase.
Hantavirus Pulmonary Syndrome
Hantavirus pulmonary syndrome occurs primarily in the southwestern US. It begins as a flu-like illness and within days produces noncardiogenic pulmonary edema. Diagnosis is with serologic tests and reverse transcriptase?PCR. Mortality is 50 to 75%. Treatment is supportive.
Most cases of hantavirus pulmonary syndrome (HPS) are caused by the Sin Nombre hantavirus (Four Corners virus, Muerto Canyon virus); others occur in patients with Black Creek Canal virus, Andes virus, or Laguna Negra virus. Infection is transmitted to humans via inhalation of excreta of sigmodontine rodents (especially the deer mouse). Most cases occur west of the Mississippi River in spring or summer, typically after heavy rains.
Symptoms, Signs, and Diagnosis
HPS begins as a nonspecific flu-like illness, with acute fever, myalgia, headache, and GI symptoms. Two to 15 days later (median 4 days), the patient rapidly develops noncardiogenic pulmonary edema and hypotension. Several patients have had a combination of HFRS and HPS. Mild cases of HPS have also been recognized.
HPS is suspected in patients with possible exposure who have unexplained clinical or radiographic pulmonary edema. The chest x-ray may show increased vascular markings, Kerley B lines, bilateral infiltrates, or pleural effusions. If suspected, echocardiogram should be obtained to exclude cardiogenic pulmonary edema. CBC, liver function tests, and urinalysis are also usually obtained. There is mild neutrophilic leukocytosis, hemoconcentration, and thrombocytopenia. Modest elevation of LDH, AST, and ALT, with decreased serum albumin, is typical. Urinalysis shows minimal abnormalities. Diagnosis is with serologic testing or reverse transcriptase?PCR.
Prognosis and Treatment
Patients who survive the first few days improve rapidly and recover completely over 2 to 3 wk, often without sequelae. Mortality is 50 to 75%.
Treatment is supportive. Mechanical ventilation, meticulous volume control, and vasopressors may be required. For severe cardiopulmonary insufficiency, extracorporal mechanical oxygenation may be life-saving.
IV ribavirin is ineffective.
Some Trade Names
VIRAZOLE
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Last full review/revision November 2005
Content last modified November 2005
http://www.merck.com/mmpe/sec14/ch191/ch191c.html
