Viral Zoonoses Slide Set

Laboratory Diagnosis of Hantaviruses Infection

D. Laboratory Diagnosis

The diagnosis of HVD is usually made on the clinical findings and serology results. In the early phase of the illness, the infection cannot be differentiated from other virus fevers. History should be sought for any possible contact with rodents.

1. Serological diagnosis - a variety of tests including IF, HAI, SRH, ELISAs have been developed
2. Direct detection of antigen - this appears to be more sensitive than serology tests in the early diagnosis of the disease. The virus antigen can be demonstrated in the blood or urine.
   
3. Virus isolation - isolation of the virus from urine is successful early in the illness. Isolation of the virus from the blood is less consistent.
    

E. Treatment and Prevention

Attentive and supportive therapy is important during the first 3 phases of the illness. Trials with ribavirin suggested a reduction in mortality if the treatment is started within the first 5 days of illness. A trial with a -interferon was not successful. HVD is mainly a disease of poverty and war. Control should be directed at reducing the contact between rodent populations and humans. An inactivated cell culture vaccine had been prepared in China where clinical trials are due to begin soon. A portion of the Hantaan virus genome has been cloned into vaccinia.
 

F. Comparative Clinical Features of Recognized Hantavirus Disease_HVD

                        Nephropathia     Far Eastern     Rat-bourne     Balkan
                        Epidermica         HVD             HVD           HVD

Virus type               Puumala         Hantaan         Seoul         Porogia

Overall Severity  .....   1-2                             2-4                         1-3                         2-4

Multiphasic Disease             occasionally                 Yes                     Blurred                     Yes

Hepatic abnormalities                 0                               0-1                         1-3                        0-1

Haemorrhagic phenomenon      0-1                             1-4                         1-2                         1-4

Mortality                                 <1%                             5-10%                     1%                     5-35%

Score = 0 to 4
 

G. Hantavirus Pulmonary Syndrome
 

A unique hantavirus has been identified as the cause of the outbreak of respiratory illness (hantavirus pulmonary syndrome) first recognized in the "Four Corners" region SW USA in 1993. The rodent reservoir is the deer mouse. Onset of the illness is characterized by a prodrome consisting of fever, myalgia and variable respiratory symptoms eg. cough followed by the abrupt onset of acute respiratory distress. Headache and GI complaints have also been documented. Overall, the mortality rate had been 62%. The pathology is essentially the same as for the classical hantaviruses whereby damage to the capilliries and blood leakage occurs. In this case, the lungs rather than the kidneys are predominantly affected. Diagnosis is usually made by the demonstration of IgM by serological tests. RT-PCR and immunehistochemistry had also been reported to be useful. Virus isolation is not an option since the virus has never been isolated from clinical specimens.Ribavirin is being currently assessed in the treatment of hantavirus pulmonary syndrome. The virus involved is most closely related to the Prospect Hill virus and is called Sin Nombre virus. Deer mouse is distributed in most parts of the U.S., parts of Canada and Mexico. The risk to campers and hikers from hantaviruses is very small, the CDC have published guidelines for reducing the risk of exposure to rodents. Hantaviruses found in other rodents such as the white-footed mouse, the cotton rat and the rice rat have also been associated with hantavirus pulmonary syndrome. At present, at least three hantaviruses are associated with the syndrome.

Link to CDC's slide set on "Hantavirus Pulmonary Syndrome and Sin Nombre Virus"    

Viral Zoonoses Slide Set