General Goal: To know the major cause(s) of Hantavirus Pulmonary Syndrome, how it is transmitted, and the major manifestations of the disease.
Specific Educational Objectives: The student should be able to:
1. describe the common means of transmission of these diseases in general and for HPS.
3. describe the major manifestations of these diseases and for HPS.
4. describe the clinical case definition of HPS.
4. describe how you diagnose, treat and prevent HPS.
Reading: MEDICAL MICROBIOLOGY by P.R. Murray, K.S. Rosenthal, G.S. Kobayashi and M.A. Pfaller, 3rd Edition. pp. 503-506.
Lecture: Dr. Neal R. Chamberlain
References:
Transmission: Diseases are usually transmitted to humans from animals or arthropod reservoirs via mosquitos, ticks, or animal urine or feces.
Incidence: Incidents are strongly focal in their occurrence and the geographic distribution coincides with various complex biological systems seasonal patterns.
Hantavirus: animal urine or feces from
mice. A total of 274 cases have been reported from May 1993 to October
2000 with a 30% fatality rate. 59% have been male, 41% female. The age
of confirmed case patients has ranged from 10 to 75 years, and the mean
age is 38 years. The distribution reflects a spring-summer seasonality
for all identified cases, although cases occur throughout the year. Cases
have been reported in 31 states, including most of the western half of
the country and some eastern states as well. Over half of the confirmed
cases have been reported from areas outside the Four Corners area.
Viral multiplication occurs in the reticuloendothelial system.
Viremia and fever occur 2-14 days after infection. It is unclear whether the virus or a viral-induced pyrogen is responsible for the fever.
Capillary lesions lead to the loss of erythrocytes and plasma into intracellular spaces.
Thrombocytopenia is also seen.
Hepatitis and severe liver damage may occur.
Focal hemorrhages: stomach, small intestine, kidneys, lungs, brain.
No inflammatory response (usually), DIC, shock with hemoconcentration (serum proteins escaping capillaries at a faster rate than erythrocytes).
High, unremittent fever in about half of the patients.
Severe myalgia
Shock and bleeding
Hantavirus = Hantavirus Pulmonary Syndrome (HPS) = An excellent description of HPS is obtain from this "site".
Patients with HPS typically present in a very nonspecific way with a relatively short febrile prodrome lasting 3-5 days. Early symptoms include fever and myalgias, headache, chills, dizziness, non-productive cough, nausea, vomiting, and other gastrointestinal symptoms. Patients may report shortness of breath (respiratory rate 26 - 30 times per minute). Typical findings include fever, tachypnea and tachycardia.
The diagnosis is rarely made at this stage. Cough and tachypnea generally do not develop until around day seven. Once the cardiopulmonary phase begins the disease progresses rapidly The patient will need to be hospitalized and usually ventilated within 24 hours.
A CBC and blood chemistry should be obtained every 8 to 12 hours if you suspect HPS.
A fall in serum albumin and a rise in the hematocrit may indicate a fluid shift from the patient's circulation into the lungs. The white blood cell count is usually raised with a marked left shift. White blood cell precursors may be as high as 50% and atypical lymphocytes are frequently present. Atypical lymphocytes usually are observed at the onset of pulmonary edema.
Platelet count in about 80% of individuals with HPS, is below 150,000. A dramatic fall in the platelet count indicate a transition from the prodrome to the pulmonary edema phase of the illness.
The following are strongly suggestive of a hantavirus infection:
An illness characterized by one or more of the following clinical features:
A febrile illness (i.e., temperature greater than 101.0 F {greater than 38.3 C}) characterized by bilateral diffuse interstitial edema that may radiographically resemble ARDS, with respiratory compromise requiring supplemental oxygen, developing within 72 hours of hospitalization, and occurring in a previously healthy person.
An unexplained respiratory illness resulting in
death, with an autopsy examination demonstrating
noncardiogenic pulmonary edema without
an identifiable cause
Detection of hantavirus-specific immunoglobulin
M or rising titers of hantavirus-specific immunoglobulin G,
or
Detection of hantavirus-specific ribonucleic
acid sequence by polymerase chain reaction in clinical specimens,
or
Detection of hantavirus antigen by immunohistochemistry.
Case classification Confirmed: a clinically
compatible case that is laboratory confirmed
Specific diagnosis is accomplished by culturing the virus from blood, throat secretion, urine, spinal fluid, or tissues.
Hantavirus = Antibodies present in patient used in an ELISA test or by PCR.
Improved sanitation standards, control of the rodent and insect vector populations.
Remember the cause of HPS (Sin Nombre virus) was just recently discovered go to this "site" for an interesting narrative of the discovery of this virus (won't be on exam).
