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Hantavirus Infection


OVERVIEW OF Hantavirus Infection :

Hantavirus pulmonary syndrome is an infectious disease characterized by flu-like symptoms that can progress rapidly to potentially life-threatening breathing problems.

Several types of hantaviruses can cause hantavirus pulmonary syndrome. They are carried by several types of rodents, particularly the deer mouse. You become infected primarily by breathing air infected with hantaviruses that are shed in rodent urine and droppings


CAUSES :

Each type of hantavirus has a preferred rodent carrier. The deer mouse is the primary carrier of the virus which is responsible for most cases of hantavirus pulmonary syndrome. Other hantavirus carriers include the white tailed mouse, cotton rat an rice rat.

Inhalational : It is the main route of transmission.

Hantaviruses are transmitted to people primarily through the aeroslization of viruses shed in infected rodent’s dropping, urine and saliva. Aerosolization occurs when a virus is kicked up into the air. making it easy for you to inhale. For example, a broom used to clean up mouse droppings in an attic may nudge into the air tiny particles of feces containing hantaviruses, which you can then easily inhale.

After you inhale hantaviruses, they reach your lungs and begin to invade tiny blood vessels called capillaries, eventually causing them to leak. Your lungs then flood with fluid, which can trigger any of the respiratory problems associated with hantavirus pulmonary syndrome.

Hantavirus pulmonary syndrome is most common in rural areas of the western United States during the spring and summer months. Hantavirus pulmonary syndrome also occurs in South America and Canada. Other hantaviruses occur in Asia, where they cause kidney disorders rather than lung problems.

The chance of developing hantavirus pulmonary syndrome is greater for people who work, live or play in spaces where rodents live. Factors and activities that increase the risk include:

  • Opening and cleaning long unused buildings or sheds
  • Housecleaning, particularly in attics or other low-traffic areas
  • Having a home or workspace infested with rodents
  • Having a job that involves exposure to rodents, such as construction, utility work and pest control
  • Camping, hiking or hunting

 


ROUTES OF TRANSMISSION :

People who become infected with the North American strain of hantavirus pulmonary syndrome aren't contagious to other people. However, certain outbreaks in South America have shown evidence of being transmitted from person to person, which illustrates variation across strains in different regions.


COMMON CLINICAL SIGNS AND SYMPTOMS :

  • Phase 1: Incubation:The virus is inhaled into the lungs. Immune cells ingest the virus, which is then transported through the bloodstream to other organs. This phase lasts 2 to 3 weeks, but there are no symptoms, yet.
  • Phase 2: Fever, dry cough, body aches, headaches, diarrhea, and abdominal pain appear. Heart and lung failure can develop during this phase, as well. Blood vessels become leaky, and fluid builds up in the lungs. Bleeding and heart failure follow. This phase lasts 2 to 8 days, and all these changes lead to shock and often death.
  • Phase 3: Changes in urination:Patients may alternate between making a lot of urine and making very little urine.
  • Phase 4: Recovery: Patients who survive the first 3 phases begin to improve, and their organs start to function properly again. It may take several weeks before patients feel completely well again. The symptoms of HPS seem to disappear as quickly and dramatically as they first appeared.

Early Symptoms

Early symptoms include fatigue, fever and muscle aches, especially in the large muscle groups—thighs, hips, back, and sometimes shoulders. These symptoms are universal.

There may also be headaches, dizziness, chills, and abdominal problems, such as nausea, vomiting, diarrhea, and abdominal pain. About half of all HPS patients experience these symptoms.

Late Symptoms

Four to 10 days after the initial phase of illness, the late symptoms of HPS appear. These include coughing and shortness of breath and feeling of tightdness in the chest.


DIAGNOSTIC :

Chest Xray:

The chest x ray predicts any abnormal area in the lungs

Computed tomography:

It reveals the slice of the lung. It uses both the combination of x ray and computer aided device.

It helps to analyse the size, shape and position of any lung tumour and also it helps in the detection of enlarged lymph nodes.

It also looks for any masses in the adrenal gland, liver, brain and other organs.

 CT guided needle Biopsy:

CT scan might be used to guide a biopsy needle into this  area to get the tissue for lung and further investigations are made.

MRI scan:

It uses the soft tissue image of the organ. It uses the both the magnet and radiowaves and aids in the view of soft tissues of the internal organs.

Immunosorbent assay- detect the virus specific IgM or IgG antibodies.

Greater than fourfold rise in titer between acute and convalescent sera  and  cerebo spinal fluid containing virus specific IgG or IgM or both are the diagnostic features.

Real time polymerase chain reaction (RT-PCR)- is valuable in the early confirmation of arbovirus infections, particularly chikungunya. However, the value of RT-PCR is limited to diagnosis in the viraemic phase, with later infection requiring serology.

Direct immunofluorescence assay -to detect chikungunya IgM has a high sensitivity and specificity and is used in the latter stages.However, the use of these tests in the tropics may be limited by financial constraints.

A normal erythrocyte sedimentation rate-  it is defined as the rate of red blood cell which are termed as erythrocytes and their deposition or sedimentation rate. The normal erythrocyte sedimentation rate is 0-22mm/hr.

 


TREATMENT AND PROGNOSIS :

As of now the cure for hantavirus causing pulmonary syndrome is treatment with the oxygen therapy, fluid replacement and medications to support blood pressure. Because of the ability to breathe can deteriorate rapidly you should be admitted to the hospital that has an intensive care unit with access to mechanical ventilation that is a respirator and kidney dialysis.

Occasionaly the physician might uses antiviral drugs, such as ribavirin, to treat other strains of hantavirus and associated infections. However, no large clinical trials have proven that these medications work.

About 4 out of 10 patients with HPS don’t survive their illness. Patients who do survive usually recover quickly. Supportive treatment during the most severe stages of the illness helps your body rest and defend itself as the virus runs its course.

With treatment, hantavirus infection resolve completely, and you can return to your normal life. No long-term (chronic) infection with hantavirus has been reported.

 


PROGNOSIS :

The prognosis of 80% can be achieved if the treatment can be started earlier.


PREVENTION :

The best treatment for HPS is to prevent infection in the first place. To do that, minimize your exposure to rodents:

  • Seal up (using cement or other patching material) holes or cracks through which rodents can enter your home or work environment. Remember, they can get through much smaller openings than you may think!
  • Identify potential nesting sites, and clean up debris, clear bushes, and trap rodents to remove them.
  • Open and air out any rodent-infested spaces that have been shut up for a long time before you enter them.
  • If you know of an area heavily infested with rodents, contact state or federal health officials about cleaning the area up.