Hantavirus Pulmonary Syndrome

　　Hantavirus Pulmonary Syndrome (HPS) is caused by Sin Nombre virus (SNV) and related Hantaviruses. The specific causes of the disease are described as follows.

　　1. Pathogen SNV is a virus belonging to the Hantavirus genus, with deer mice as its host.

　　2. Modes of Transmission It is not clear. It may be transmitted like other Hantaviruses, through the feces, urine, and saliva of rodents, which are inhaled by humans as aerosols or particles, leading to illness.

　　3. Epidemiological situation and influencing factors Hantavirus Pulmonary Syndrome has occurred in at least 30 states in the United States, and in recent years, cases have also been reported in Germany, Sweden, and other European countries. An increase in contact between humans and rodents is one of the important factors, and therefore, the occupational risk is attracting attention.

　　Severe patients with Hantavirus Pulmonary Syndrome may develop complications such as hypotension, shock, heart failure, and arrhythmias such as sinus bradycardia or sinus tachycardia. Only a few patients may have conjunctival congestion, bulging of the bulbar conjunctiva, bleeding spots on the skin and mucous membranes, or ecchymosis.

　　The typical course of Hantavirus Pulmonary Syndrome (HPS) is divided into three phases: prodromal period, cardio-pulmonary phase, and recovery period. The specific clinical manifestations are described as follows.

　　1. Prodromal period

　　Patients often have an acute onset, with prodromal symptoms such as chills, fever, myalgia, headache, and fatigue. Gastrointestinal symptoms such as nausea, vomiting, diarrhea, and abdominal pain may also be present. Fever is generally 38～40℃, and the above symptoms may last for 12 hours or less, averaging 3～6 days.

　　2. Cardio-pulmonary phase

　　Most patients rapidly develop cough, shortness of breath, and respiratory distress within 2 to 3 days and enter the respiratory failure period, which is non-cardiogenic pulmonary edema. Physical examination may show: increased breathing rate, increased heart rate, coarse or fine moist rales in the lungs, and a few patients may have pleural effusion or pericardial effusion. Severe patients may experience hypotension, shock, heart failure, and arrhythmias such as sinus bradycardia or sinus tachycardia. Only a few patients may have conjunctival congestion, bulging of the bulbar conjunctiva, bleeding spots on the skin and mucous membranes, or ecchymosis.

　　3. Recovery period

　　Patients who can survive the respiratory failure period gradually enter the recovery period, at this time the breathing is stable, oxygen deficiency is corrected, and only a few patients may still have persistent low fever and physical strength may take some time to recover. However, some patients may not show symptoms of pulmonary syndrome.

　　To prevent Hantavirus Pulmonary Syndrome, it is necessary to prevent the cause of the disease and cut off the source of infection. The specific preventive measures are described as follows.

　　First, rat prevention and control Use drugs or mechanical methods to eliminate rats, and establish rat-proof facilities in the home.

　　1. Place drain nets:Add wire mesh at the inlets and outlets of the drain, with mesh openings not greater than 0.6*0.6 cm to prevent rats in the drain from moving up and down in the pipes. The open ditches in the kitchen of the catering industry should be covered with a mesh or other items to prevent exposure.

　　2. Set up rat-proof doors:The lower part of the door (frame) can be inlaid with iron sheet 40 cm high to prevent rats from gnawing through the door panel (frame).

　　3. Narrow down various gaps:Repair the gaps between the door and the ground, the door and the door, and the window and the sill, so that the gaps are not greater than 0.6 centimeters to prevent the house mouse from sneaking in. Set up rat guards, add a door sill 60 cm high at the bottom of the door, and keep the rats out of the door.

　　4. Hardening the ground:Promptly repair broken, unhardened ground, or harden the road surface to prevent rats from digging holes and making nests.

　　Second, pay attention to personal hygiene Zoologists and field biologists should try not to touch rodents and their excrement with their hands. Medical personnel should pay attention to isolation when contacting patients.

　　3, Vaccine The currently developed Hantavirus HanTan and HanCheng type vaccines have no cross-protective immunity between different types of Hantavirus Pulmonary Syndrome, so it is necessary to continue to develop effective vaccines.

　　The examination of Hantavirus Pulmonary Syndrome includes laboratory examination and other auxiliary examinations, and the specific detection methods are described as follows.

　　1, Laboratory examination

　　The majority of patients with the disease have an increased white blood cell count, up to (30-65) x 10^9/L. Neutrophils are significantly elevated, with left shift. Immature lymphocytes, late blast cells, and/or intermediate blast cells may appear, and atypical lymphocytes are also common. Platelets are significantly reduced, and some patients have blood concentration, with increased red blood cells and hemoglobin, and increased hematocrit.

　　2, Other auxiliary examinations

　　1, Patients with kidney damage Proteinuria and microscopic hematuria may occur, and the urine protein is generally ++.

　　2, Blood biochemical examination Alanine aminotransferase (ALT), aspartate aminotransferase (AST) elevation and hypoalbuminemia, in addition, lactate dehydrogenase (LDH) and creatine kinase are often significantly elevated. In patients with kidney damage, blood urea nitrogen and creatinine increase, and a few patients have metabolic acidosis.

　　3, Arterial duct examination Low pulmonary artery wedge pressure and significantly reduced cardiac index suggest non-cardiogenic pulmonary edema.

　　4, X-ray examination Interstitial infiltrative shadows or infiltrative shadows in both lungs or interstitium and alveoli can be seen, and some patients may have pleural effusion and pericardial effusion.

　　5, Bronchoscopy No abnormalities were found in the airway, no bronchial mucosal damage was found, and a few patients had erythema in the airway. The total protein, albumin, and lactate dehydrogenase in the tracheal aspirate were significantly increased, even reaching or exceeding serum levels.

　　Thrombosis function examination

　　There may be prolonged partial thromboplastin time (WBPTT) and prothrombin time, and a small number of patients may have elevated fibrin degradation products, but normal fibrinogen.

　　Patients with Hantavirus Pulmonary Syndrome should eat foods with lung-nourishing effects; eat foods that enhance immunity; eat foods that promote expectoration. It is taboo to eat heavy foods; it is taboo to eat sticky foods that are not easy to swallow; it is taboo to eat cold foods.

　　There is no specific treatment for Hantavirus Pulmonary Syndrome. Ribavirin can be used in the early stage of the disease, but it is ineffective after entering the cardiovascular phase. Current treatments are all supportive, especially respiratory and circulatory support. Routine oxygen therapy and mechanical ventilation can be used. The specific treatment methods are described as follows.

　　Considering that the disease progresses rapidly after onset and has a very high mortality rate, clinical suspected cases should be carefully monitored and observed for respiratory rate, heart rate, blood pressure, and other conditions. Since the disease broke out and spread in Argentina, epidemiological studies have suggested the existence of human-to-human transmission, therefore, patients should be strictly isolated.

　　26. After onset, early bed rest should be maintained, and appropriate fluid should be supplemented. Balanced salt solution and glucose saline can be administered intravenously. For patients with high fever, physical cooling is the main method, and intravenous drip of glucocorticoids can also be given.

　　25. For hemorrhagic fever with renal syndrome caused by Hantavirus HTNV and SEOV type infection, the early application of ribavirin for anti-infection treatment is effective, and therefore the US CDC has approved the use of ribavirin in the early stage of the disease.

　　24. When dyspnea or hypoxemia occurs in clinical practice, oxygen should be administered in time, and nasal cannula or face mask can be used for oxygen inhalation. Sedatives should be given to patients who are restless. If the condition worsens or oxygen inhalation is ineffective, and the arterial oxygen concentration remains below 8.0kPa (60mmHg), mechanical ventilation should be used in time. Artificial respirators are used for positive end-expiratory pressure ventilation until clinical symptoms improve. In addition, it is advocated to use high-dose glucocorticoids to reduce the permeability of pulmonary capillaries, relieve bronchospasm, stimulate the synthesis and secretion of pulmonary surfactant by type II alveolar cells, and alleviate alveolar atrophy. Dexamethasone 30-60mg/d can be administered intravenously.

　　23. When hypotensive shock occurs, blood volume should be replenished in time, and balanced salt solution, dextran 40, mannitol, or human serum albumin can be used. During the expansion period, blood pressure changes should be closely observed, and the infusion rate should be adjusted. If the blood pressure still cannot be maintained after repletion, attention should be paid to correcting acidosis, and vasoactive drugs such as dopamine may be administered intravenously as necessary. After the blood pressure returns to normal, continuous infusion for more than 24 hours is still required.

　　22. For those with oliguria and renal failure, water intake should be restricted, and the daily water intake should be the urine output plus vomiting volume of the previous day plus 700ml. In addition to using 5% sodium bicarbonate injection to correct acidosis, hyperosmotic glucose injection is mainly infused to supplement energy, reduce intracellular metabolism, and control the rise of azotemia. In addition, furosemide intravenous injection can be used to promote diuresis. If oliguria persists for 4 days or anuria for more than 24 hours, and the blood urea nitrogen is greater than 28.56mmol/L, hemodialysis treatment may be considered.