Robinson, Jennifer
Lab Section CRA

Disease

Hantavirus Pulmonary Syndrome

Causative Agents

            Hantaviruses are viruses belonging to the Bunyavirus family.  Bunyaviridae are typically known to be enveloped viruses ranging from 90 to 100 nanometers in diameter.   Specifically the virion of the Hantavirus  is reported  as 98 nm in diameter by www.virology-online.com .  These spherical shaped viruses have single-stranded RNA.  Their life cycle includes replication in the cytoplasm and budding either at or within the area of the Golgi (Shope, Medical Microbiology).   The Hantavirus organisms are passed to humans by interaction with infected rodent feces or bodily fluids.  They cause two severe diseases,  hemorrhagic fever with renal syndrome (HFRS)  and hantavirus pulmonary syndrome (HPS).    

Epidemiology

            The typical host responsible for passing HPS to humans are infected rodents, particularly the deer mouse in North America.   In 1993-1994, a new form of lethal pneumonia emerged in the southwestern United States.  The outbreak showed symptoms that were consistent with the typical signs of hemorrhagic fever with renal syndrome such as kidney failure, very high fevers, and hemorrhaging, however this new strain was accompanied by serious pulmonary symptoms.  (Medical Update, Nov 1994).   The same publication also suggests that HPS was formed by a mutation in the hantaviruses,   which now placed the primary site of infection in the pulmonary system.    The strain of hantaviruses responsible for HPS is mainly the Sin Nombre Virus (SNV)  which is usually found within the North and South American continents. Other hantavirus strains are known to cause infection throughout the world,  but again the SNV strain seems to be limited to the Americas  (Cunha, 2008).  

            HPS infections tend to affect individuals who are more likely to encounter areas contaminated by infected rodents.   Race or sex has no determining factor for acquiring the disease and there have been no documented cases of HPS being transmitted from human to human, except for the possibility of one strain that was restricted to an outbreak  in Argentina (species Andes Virus)  (Cunha, 2008).    From 1993 to 1997 there were 465 documented cases of HPS in the U.S.    Out of the 50 states,  33 have reported HPS presence.    The report shows that as of March 2007,  35% of of the 456 documented cases were fatal.   The ages of the individuals affected ranged from around 10 to 83 years and the mean age was 38  (Dhawan & Mas Casullo,  eMedicine 2008).

Transmission

            As noted above,  HPS and other hantaviruses are transmitted to humans by contact with infected rodent feces, saliva, and urine. The primary route of infection by the Sin Nombre Virus found in the U.S. Is  the white footed deer mouse.  Rodents are found to carry the virus for long periods or possibly for the entire life span.  The infected rodents secrete airborne particles in the bodily fluids as well as dried fecal matter.    These particles enter humans through inhalation into the respiratory system.  Bites from infected animals may transmit the virus as well (www.microbewiki.com).   HPS  can also be spread by ingesting foods that have been contaminated by infected rodent saliva, urine, or feces.

Signs and Symptoms

            HPS presents itself in a series of clinical phases.   Once an individual has been exposed,  the typical incubation period can range from 1-4 weeks.  Incubation ends when the first of the three infection  phases begins.   This is known as the prodromal (def)  phase which can include many of the same symptoms associated with other more common  viral infections.  This can include myalgia (def), dizziness, gastrointestinal upset (vomiting, diarrhea, nausea),  severe abdominal pain, and fever.   Typically this stage lasts 3-5 days, there is a lack of respiratory symptoms,  and most diagnostic tests (labs, chest X-ray, ect.) may be relatively negative.   During the early period of infection,  HPS may be misdiagnosed with a more common illness like influenza or a gastrointestinal viral infection (Cunha) (Vanderford).

            According to Virology-Online.com,  respiratory symptoms begin with a sudden onset during the second (cardiopulmonary) phase.   This short stage (1-2 days) is marked by a cough that is non-productive and progressively gets worse along with dyspnea (def).   Fever is still present and other physical findings may include tachycardia (def), a drop in blood pressure (hypotension),  and tachypnea (def) (Vanderford).  Lung and pleural (def) edema (def)  may be present due to increased permeability of the capillaries.  This can increase the risk for cardiac and renal malfunction as well as hypoxemia (def).   According to a publication Hantavirus Pulmonary Syndrome:  Treatment & Medication,  approximately  25% of affected patients may require the use of ventilators and intubation during hospitalization according due to the severity of cardiopulmonary symptoms.   Failure to improve during this phase, can be fatal due to circulatory or respiratory failure (Cunha).

The latent phase of HPS, is the convalescent stage.   Following treatment, improvement can be rapid and the use of mechanical ventilation can be stopped.   The affected are closely monitored  and tend to have no residual issues following HPS once fully recovered (Cunha).

Prevention and Treatment

            Treatment for HPS consists of respiratory and cardiac support, as well as close monitoring of fluid balance by the attending physician.    Currently, there is no vaccine available for HPS.  During acute illness, intubation and ventilation may be necessary for pulmonary symptoms.   For blood pressure and cardiac output stability, medications such as  pressor agents and inotropic agents may be used (Vanderford).   An antiviral drug Ribavirin has been used and may reduce mortality if given during early onset of symptoms (Dhawan & MasCasullo).   Consultations with infectious disease specialists as well as pulmonary specialists may be warranted.

             Prevention of HPS consists of common-sense techniques to avoid contact with areas that are frequented by rodents.    Care should be taken when removing or handling deceased animals such as masks and gloves.   Proper rodent control measures are  necessary and avoiding unventilated areas that may be inhabited by rodents, especially when sweeping or disturbing objects that may cause particles to become airborne.
           

Bibliography

Cunha, Bruce A. (Updated June 25, 2008). Hantavirus Pulmonary Syndrome.  Retrieved March   31, 2010 from http://emedicine.medscape.com/article/236425

Cunha, Bruce A. (Updated June 25, 2008). Hantavirus Pulmonary Syndrome: Treatment &             Medication. Retrieved March 31, 2010 from http://emedicine.medscape.com/article/236425-treatment

Dhawan, V. & MasCasullo, V. (Updated August 11, 2008). Hantavirus Pulmonary Syndrome. Retrieved April 16, 2010 from http://emedicine.medscape.com/article96443

Hantavirus. (n.d.) Retrieved from http://microbewiki.kenyon.edu/index.php./Hantavirus

Hantaviruses: Viral Zoonoses Slide Set (n.d.). Retrieved April 13, 2010 from http://virology-            online.com/viruses/Hantavirus.htm

Shope, Robert E. & Baron, S. (Eds). (n.d.).  Medical Microbiology: Bunyaviruses.  Retrieved
from http://www.ncbi.nih.gov/bookshelf/br.fcgi?book=mmed&part=A2986

“The hantavirus – an old enemy with a new look.”  Medical Update  Nov. 1994:2. Academic One File.  Retrieved  April 9, 2010 from                     http://find.galegroup.com.ezproxy.aacc.edu/gtx/printdoc.do?conentSet=IAC-            Document&type=retrieve&tabID=T004&prodId-            AONE&docId=A15998394&source=gale&srcprod=AONE&userGroup

Vanderford, Virginia. Hantaviruses: An Overview and Radiographic Correlation."  Radiologic      Technology 70.4 (1999): 373 Academic OneFile.  Retrieved April 9, 2010 from
http://find.galegroup.com.ezproxy.aacc.edu/gtx/informak.do?&contentSet=IAC-            Document&type=retrieve&tabID=T002&prodId=AONE&docId=A5426038&source-            gale&srcprod=AONE&userGroup