Review understanding of hemorrhagic fever with renal syndrome

 Not long ago, "Xi 'an hemorrhagic fever" entered the hot list. Hemorrhagic fever is a kind of infectious disease caused by viral infection with fever, hemorrhage and shock as the main manifestations. These diseases are widely distributed in the world, with severe clinical manifestations and high mortality. At present, more than 10 species have been found in the world, including Crimean-Congo haemorrhagic fever, Ebola haemorrhagic fever, Marburg haemorrhagic fever, Lassa fever, Rift Valley fever, dengue haemorrhagic fever and yellow fever. This cause people's concern is hemorrhagic fever with renal syndrome, also known as epidemic hemorrhagic fever, is caused by various types of hantavirus viruses, to mice as the main source of infection of a natural epidemic disease, mainly distributed in Asia.

Hantavirus has been reported or detected in 78 countries worldwide. The disease was first recorded in 1913 in Vladivostok (now known as Vladivostok) of the Soviet Union. Hemorrhagic fever with renal syndrome occurred in The Invading Japanese army and Russian army at the Sino-Russian border in Heilongjiang Valley from 1931 to 1932. From 1938 to 1942, more than 300 Japanese soldiers in training exercises in Erdaogang, Sunwu, Heihe and Hulin areas of Suifenhe Valley in northeast China fell ill and dozens died. They were called "Erdaogang fever", "Sunwu fever", "Heihe disease" and "Hulin fever".

China's provinces, autonomous regions and municipalities directly under the Central Government have the disease. The disease occurs in China's altitude of 500 meters below the area, the epidemic area is mainly distributed in the rich water zone, multiple water zones and transitional zone of agricultural areas (such as Shandong, Shaanxi, Hubei, Hunan, Zhejiang, Jiangsu, Jiangxi and Anhui provinces) and northeast forest (such as Heilongjiang Province). According to the data and literature of the National Monthly Report on Notifiable diseases of the National Health Commission, a total of 1,688,031 cases of hemorrhagic fever with renal syndrome (HFRS) have been reported in China from 1950 to the end of 2020, among which 48,260 died. The annual fatality rate fluctuated from 0.60% to 13.97%, and the overall fatality rate reached 2.86%.

The disease occurs in all months of the year, with peak incidence in spring and autumn and winter. The peak of apodemus spreaders was from November to January of the next year, and the small peak was from May to July. The peak of mouse transmission was from March to May. The incidence of this disease has periodic fluctuations. The epidemic areas with Apodemus as the main source of infection generally have a large epidemic several years apart, while the periodicity of the epidemic areas with house rat and yellow squirrel as the source of infection is not clear.

After entering the human body, the virus mainly replicates in vascular endothelial cells, which can directly damage vascular endothelial cells, leading to systemic small vascular lesions, increased vascular permeability, plasma extravasation, resulting in blood concentration, decreased effective blood volume, decreased blood pressure, and increased risk of subcutaneous and visceral bleeding. The injury of vascular endothelial cells, coupled with the deposition of immune complexes produced by immune response in the kidney, can lead to acute renal impairment.

The clinical manifestations of this disease are very characteristic, and experienced doctors can often make a rapid diagnosis of suspected and timely diagnosis. The incubation period of this disease is 4 ~ 46 days, generally 7 ~ 14 days, with 2 weeks more common. Typical cases have acute onset, and the course of disease includes three main symptoms: fever, bleeding and renal impairment, and five stages: fever, hypotensive shock, oliguria, polyuria and recovery, but the number of atypical cases is increasing significantly.

The febrile period is mainly characterized by fever, systemic poisoning symptoms, capillary damage and kidney damage. The typical characteristics of this period are "three red and three pain". Systemic poisoning symptoms for systemic pain, headache, lumbago, orbital pain (" three pain "); Capillary lesion is mainly manifested as hyperemia, hemorrhage and exudation edema. Severe cases can see obvious eye conjunctiva edema, congestion, bleeding, accompanied by acute pain face, often bring fear to family members and patients; Severe edema and exudation of the mesentery can lead to persistent abdominal pain and greater pain for the patient. Skin flushing is mainly seen in the face, neck, chest (" three red ") and other parts, serious people are "drunk appearance". Renal damage in fever stage is mainly manifested in proteinuria and tubular type can be found by microscopic examination. In severe cases, white floc can be seen in urine, which is called "tubular type". Among them, "three red and three pain" are important symptoms and signs for early diagnosis of hemorrhagic fever, and typical symptoms appear in fever period. Clinicians should be alert to the disease and timely improve the etiological examination, which is conducive to early diagnosis and treatment, reduce the risk of serious complications, and avoid treating it as a "common cold", delaying treatment, delaying the condition and bringing adverse consequences.

Hypotensive shock phase generally occurred in the onset of the disease 4-6 days, as late as 8-9 days. In most patients, blood pressure decreased at the end of fever or heat retreat, and a few at the end of heat retreat. When blood volume drops, there is pallor, cold limbs, weak or inaccessible pulse, reduced urine volume and other symptoms. Acute respiratory distress syndrome, extensive bleeding and other serious complications may occur in the shock stage, and the duration of the shock stage is related to the severity of the disease. This stage of clinical symptoms is difficult to distinguish from septic shock.

Oliguresis often followed hypotensive shock period, generally 24 hours less than 400 ml urine, less than 50 ml for no urine. The main manifestations are uremia, acidosis and water and electrolyte disorder, and severe patients may have hypervolemic syndrome and pulmonary edema. Clinical manifestations are anorexia, nausea, vomiting, abdominal distention and diarrhea, etc., often intractable hiccup, dizziness, headache, irritability and lethargy, delirium and even coma. The length of oliguria period is the main reason to determine the speed of recovery.

In polyuria stage, the daily urine volume gradually increases from 400 ml to 4000 ~ 8000 ml, which is prone to hypokalemia. In the convalescence period, urine volume restored to 2000 ml below, spirit appetite basic recovery. There is still a risk of visceral hemorrhage in polyuria and convalescence. It usually takes one to three months to regain full strength.

The renal function damage of this disease is usually reversible, and the most dangerous complication is hemorrhage, especially intracranial hemorrhage, pulmonary hemorrhage and digestive tract hemorrhage, which can often endanger life. Patients in critical condition may have refractory shock, bleeding in important organs, long duration of oliguria/anuria, heart failure/respiratory failure, cerebral edema/hernia, and secondary severe infection.

Mild patients only present with mild fever and may not have a typical five-stage course. Severe cases may present warning symptoms: body temperature of more than 40 degrees Celsius or heat course of more than 1 week, frequent and severe nausea and vomiting, irritability, delirium or disturbance of consciousness, severe bulbar conjunctiva edema, obvious bleeding tendency, peripheral blood white blood cell count & GT; 30×109/ l, platelet count < 20×109/ l, human blood albumin < 15 grams per liter.

When severe warning signs occur, patients' vital signs should be closely observed, and blood white blood cell count, platelet count, human albumin and hemoglobin should be monitored.

Network rumor this "Xi 'an haemorrhagic fever" and "eat strawberry" related, "eat strawberry" after all can get haemorrhagic fever?

As a natural epidemic disease, haemorrhagic fever virus is mainly in the body of infected animals and the environment of animal activities. According to incomplete statistics at home and abroad, more than 170 vertebrates can naturally infect Hantavirus, and 53 species of animals have been found to carry hantavirus in China. The main host animals are rodents (most commonly rats), and other animals include cats, pigs, dogs and rabbits. Apodemus agrarius and Rattus norvegicus were the main host animals and sources of infection in China. The forest area is dominated by apodemus dauricus.

There are five main ways of transmission of HFRS. (1) respiratory transmission: the feces of mice carrying the virus, such as urine, feces, saliva and other pollution dust formed aerosol, can infect the human body through the respiratory tract; (2) Digestive tract transmission: eating food contaminated by the feces of rodents carrying the virus can be infected by oral or gastrointestinal mucosa; ③ Contact transmission: bitten by rats or broken wounds in contact with the feces or blood of mice with the virus can also lead to infection; (4) vertical transmission: pregnant women infected with the disease after the virus can infect the fetus through the placenta; (5) Arbo-borne transmission: Although hantavirus has been isolated from chigger mite and Cypress mite in China, its transmission needs to be further confirmed.

So in theory if strawberries on strawberry farms were contaminated by rats, people who ate them could get infected through the digestive tract. But this is all speculation, not direct objective evidence. According to the data released by The Chinese Center for Disease Control, in the past 30 years, the annual reported cases of hemorrhagic fever in Shaanxi have been in the forefront of the country, and it is itself an area with high incidence of hemorrhagic fever. Therefore, it is not scientific to ascribe the transmission route of "Xi 'an hemorrhagic fever" to "eating strawberries". In recent years, with the rapid development of "we media", many spokesmen lack news professionalism and lack comprehensive consideration. Therefore, they should be cautious and objective about online rumors. The Chinese Center for Disease Control has confirmed that the source of infection of the haemorrhagic fever is Apodemus agrarius, contact with infected apodemus agrarius excrement, secretions contaminated food, aerosol and other people may be infected.