Hantavirus Pulmonary Syndrome

Hantavirus Pulmonary Syndrome or HPS is a severe, but not commonly occurring respiratory disease in humans caused by a rare type of infection carrying Hantavirus. It is proved that, rodents carry this fatal Hantavirus and humans who come in contact with these rodents are at risk of getting Hantavirus Pulmonary Syndrome. The infection with Hantavirus can attack even healthy persons at any time if they remain exposed to rodent infestation for a longer period.

Several researches have been carried out on Hantavirus Pulmonary Syndrome in USA and other parts of the world, but no trace of person-to-person transmission of Hantavirus Pulmonary Syndrome has been detected till now. The disease is not a common one, but it can be fatal if not treated on time.

Hantavirus Pulmonary Syndrome

Signs and Symptoms of Hantavirus Pulmonary Syndrome

Normally, symptoms of Hantavirus Pulmonary Syndrome start to expose after two to three weeks of getting affected by this Hantavirus.

Early symptoms may include:

  • Fever, Chills, muscular aches and headache
  • Fatigue without any apparent reasons.
  • Nausea, vomiting, and diarrhea.
  • Feeble to severe belly pain.

These symptoms start to appear after two to three weeks and right after these minor symptoms many other serious physical problems outbreak. Some of those are as follows –

  • Dyspnea frequently leading to respiratory failure
  • Shortness of breath along with coughing.
  • Increase of heartbeat
  • Fast breathing.

All these above mentioned issues start appearing too fast not giving the patients or families to understand the problem or take decision to bring the patients to the hospital. Right after breathing trouble starts with a cause of Hantavirus Pulmonary Syndrome, patients may die due to the infection within a maximum period of two days.

Occurrence of Hantavirus Pulmonary Syndrome

In USA alone, almost 660 cases of Hantavirus Pulmonary Syndrome are identified since 1993. Almost 35% of all these cases resulted in death. Compared to females, males are more prone to Hantavirus Pulmonary Syndrome. As per the statistics available in USA, 63% of Hantavirus Pulmonary Syndrome are detected in males.

Few other interesting statistics of Hantavirus Pulmonary Syndrome are –

  • It is found at all ages of human, ranging from 5 to 84 years.
  • Among the affected people, 78% are whites in USA.
  • 20% cases are detected in American Indians.
  • 1% of cases are detected in Asian and 1% in Africans residing in USA.

Poor record maintenance in other countries is the main impediment in further researches on HPS. Outside USA, very few cases are reported officially. Some individual cases are found in Argentina, Brazil, Chile, Panama, Uruguay and Venezuela etc.

Prognosis and Mortality Rate of Hantavirus Pulmonary Syndrome

There is almost 36-40% mortality rate in Hantavirus Pulmonary Syndrome. Problems intensify due to delayed detection of the Hantavirus syndrome.

In mild cases of Hantavirus Pulmonary Syndrome, the prognosis is quite satisfactory and can recover without any residual cardiopulmonary sequelae. However, it often becomes difficult to diagnose the condition in initial stages as many patients remain unaware that they have even come in contact with rodents that carry the virus. Patients with this syndrome in advanced stage have poor prognosis.

Causes of Hantavirus Pulmonary Syndrome

In most of the cases, Hantavirus Pulmonary Syndrome is caused by only one type of Hantavirus, viz. ‘Sin Nombre Virus’ found in the rodent.

Some detected causes of spreading of HPS are as follows -

  • Touching urine, excreta and saliva of rodent.
  • Rodent’s urine spreads tiny aerial particles. Breathing such particles may cause the Hantavirus to enter into human lungs.
  • Even dust contaminated with Hantavirus can be a cause of this disease.
  • Biting of rodents already infected with the Hantavirus can cause Hantavirus Pulmonary Syndrome.

Apart from rodent, no other animals are known to carry this Hantavirus. Hence, researchers are beyond doubt that the pet animals or cattle are absolutely safe from this particular type of Hantavirus.

Person-to-Person Transmission of HPS

While investigating some cases of respiratory problems in 1993 in South-Western part of USA, researchers discovered the existence of previously unknown Hantavirus called ‘Sin Nombre Virus’ or SNV. It was the sole reason behind that respiratory syndrome, which was named as Hantavirus Pulmonary Syndrome. Transmission of the Hantavirus is primarily attributed to inhalation of aerosolized rodent excreta. Later, it was found that rodent’s urine and dust around the animal can also spread the disease. It is also proved by the researchers that HPS has a prominent pulmonary component, which suggests the ability of the Hantavirus to spread through inhalation of the aerial particles carrying the Hantavirus. Till to-date no evidence is found where it could be proved that Sin Nombre Virus gets transmitted through infected humans for the North American version of the syndrome. However, certain milder of the South American type of the syndrome could be contagious.

Incubation Period and Stages of Hantavirus Pulmonary Syndrome

The Hantavirus takes almost 2-3 weeks for developing and showing symptoms. The course of the disease can be broadly divided into three stages –

  • Stage 1 of Hantavirus Pulmonary Syndrome: This stage is called ‘Prodromal Stage’ when patients start to show some normal symptoms like fever and headache etc. Except mild dizziness and fatigue no other neurological symptoms are detected.
  • Stage 2 of Hantavirus Pulmonary Syndrome: This is the ‘Cardiopulmonary phase’, when the patients start to show dyspnea, shortness of breath, faster heart beats, non-productive cough etc. In majority of cases, at this stage mechanical ventilation is required.
  • Stage 3 of Hantavirus Pulmonary Syndrome: This stage is called ‘Convalescent Phase’ when through proper treatment the symptoms starts to disappear. The improvement takes place quite rapidly. Patients are released from the hospital within 7-10 days of this stage, but follow-up is strongly advised by the doctors.

Diagnosis for Hantavirus Pulmonary Syndrome

Early diagnosis of Hantavirus Pulmonary Syndrome is really difficult, because most of the above mentioned syndromes closely resemble to normal influenza. It depends on the medical practitioner’s experience to doubt the spread of infection in the visiting patient with such symptoms. If the patient is complaining of fatigue, fever, and body aches along with breathing problem and also has a history of handling rodents for sometimes, the doctor may doubt it as a case of Hantavirus Pulmonary Syndrome. In such circumstances, the patient should be bought to a hospital at the quickest possible time, because the Hantavirus proliferates in human body too fast.

Doctors undertake different pathological tests depending on the severity of the disease. Chest X-ray, oxygen saturation test, and complete blood count are quite normal tests in of Hantavirus Pulmonary Syndrome.

Differential Diagnosis of Hantavirus Pulmonary Syndrome

Differential diagnosis is very much essential for Hantavirus Pulmonary Syndrome.

It is needed to differentiate between non-cardiac pulmonary edema from Hantavirus Pulmonary Syndrome. In the former case, patients normally shows gallop rhythm in left ventricular S3, but in case of Hantavirus Pulmonary Syndrome galloping rhythm in that part of the heart is not detected.

Again, HPS is also clinically differentiated with Acute Respiratory Distress Syndrome. It is observed through chest X-rays that infiltrates concentrates on peripheral regions while in case of Hantavirus Pulmonary Syndrome pleural effusion in central region is more common. Apart from formation of pleural effusion, Hantavirus Pulmonary Syndrome is associated with the following –

  • Peribronchial Cuffing
  • Pericardiac Haziness
  • Intestinal edema.

These three occurrences are not associated with Acute Respiratory Distress Syndrome.

Symptoms of Hantavirus Pulmonary Syndrome closely resembles Legionnaires’ disease also, but some differences are there like the following –

  • Legionnaires’ disease is accompanied with uniform ‘Relative Bradycardia’ which doesn’t happen in case of Hantavirus Pulmonary Syndrome.
  • Renal insufficiency is quite common in Legionnaires’ disease which is not so in HPS.
  • Cardiopulmonary collapse is associated with Hantavirus Pulmonary Syndrome, which is not so obvious in Legionnaires’ disease.

Hantavirus Pulmonary Syndrome also needs to be differentiated from Pneumonic Plague. The former is strongly associated with Hemoptysis and usually Pneumonic Plague follows the outbreak of Bubonic Plague.

Two common zoonotic atypical pneumonias, viz. Q fever and Tularemia are also considered in differential diagnosis of HPS. The basic differences are as follows –

  • Q fever appears only in contact with sheep or parturient cats carrying the infection.
  • Tularemia spreads in contact of deer flies, rabbits or deer carrying the infection.
  • Q fever features uniform relative bradycardia and splenomegaly, which don’t occur in Hantavirus Pulmonary Syndrome.
  • Pleural effusion with blood is common in Tularemia which doesn’t occur in Hantavirus Pulmonary Syndrome.

Differential diagnosis helps to detect Hantavirus Pulmonary Syndrome more quickly and exactly, which helps the doctors to start proper medication at the earliest.

Treatment of Hantavirus Pulmonary Syndrome

There is no specific treatment procedure followed in Hantavirus Pulmonary Syndrome. No vaccine is available as safeguard. Diagnosis of the disease at the early stage can prevent the growth of fatal symptoms. Hospitalization of the patients is necessary at the later stages, when they are kept under intensive care with mechanical ventilation. Hence, earlier the patient is brought under medical supervision, the better it is for the patients. Patients are often given oxygen therapy to relieve the pulmonary distress. However, if the distress is very high, treatments are of little use.

Medical history and day-to-day activities of the patient should be brought in to attention of medical practitioner. Fever and other symptoms, if followed by the close contact with rodents, should be informed to the doctor. This will allow the doctor to take necessary diagnosis procedure for detecting Hantavirus Pulmonary Syndrome.

Prevention of Hantavirus Pulmonary Syndrome

Since the disease is primarily caused by rodents, the best way to prevent the disease is by avoiding the animal. In case, if somebody needs to visit the area with many rodents roaming around, it is better to take all possible protection like mask, rubber gloves and gumboots.

Some precautions to take during working with rodents like trapping them or blocking their free movements’ are–

  • Use of traps is necessary to catch the rodents.
  • Daily garbage at home needs to be kept in tight container so that rodents couldn’t come to get their foods from the garbage.
  • Cleaning the site in a house where rodents frequently move is necessary. Mere cleaning will not work. It is better to call professional people. In case no such professional is available, it is feasible to take maximum precaution before cleaning.
  • It is always necessary to visit a closed room or place in a house or garden only after cleaning the place properly and airing out the closed room.

Conclusion

Hantavirus Pulmonary Syndrome is quite deadly in nature. If detected in time, it can be eradicated completely with no residual cardiopulmonary sequelae. The main hindrance of early detection of HPS is its early symptoms. These symptoms resemble with normal influenza and in some advanced stages too, symptoms are often perplexing. It is always advisable to take proper precautions while handling rodents, and better to avoid the animal. While having influenza like symptoms after handling rodents, patients should be brought under medical care to get perfectly investigated for HPS. The apparently fatal Hantavirus spreads too quickly giving little time for diagnosis and treatments. Thus, one must not delay in seeking help if the symptoms arise.

Written, Edited or Reviewed By:

, MD, FFARCSI

Last Modified On: August 20, 2016

Pain Assist Inc.

Pramod Kerkar
  Note: Information provided is not a substitute for physician, hospital or any form of medical care. Examination and Investigation is necessary for correct diagnosis.

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