Renal syndrome hemorrhagic fever is a highly contagious, fast-spreading disease, also known as epidemic hemorrhagic fever, referred to as "hemorrhagic fever", caused by hantavirus. Seeing this, you may feel that these disease names and "hantavirus" are very strange and very far away from yourself, but in fact, the source of renal syndrome hemorrhagic fever is an animal that we are very familiar with, that is, mice.
On the mainland, brown rats and haddock rats are the most important sources of hemorrhagic fever infection for renal syndrome. Infected animals are recessively infected, do not have the disease, but are detoxified, contain viruses in their excrements and secretions, and are contagious.
Hemorrhagic fever in renal syndrome is widely distributed on the mainland, with high incidence and mortality rates, and is a very great threat to working people. For renal syndrome hemorrhagic fever, this knowledge should be understood.
I. Research progress of hemorrhagic fever in renal syndrome
1. What is renal syndrome hemorrhagic fever?
Renal syndrome hemorrhagic fever is a natural epidemic infectious disease caused by hantavirus, and the clinical features are mainly high fever, hypotension, congestive bleeding and renal damage, and complications and atypical cases are often present. The World Health Organization officially named epidemic haemorrhagic fever as renal syndrome haemorrhagic fever in 1982.
In mainland China, brown rats and haddock rats are the main host animals for renal syndrome hemorrhagic fever, of which haddock rats are the main source of infection for hemorrhagic fever, and brown rats are the main source of hemorrhagic fever in domestic mice. Most patients develop the disease as a result of exposure to such animals or their feces and secretions. The disease is widely distributed in the mainland, the incidence and mortality rate are high, and the threat to working people is greater.
2. Epidemiological features of hemorrhagic fever in renal syndrome
Hemorrhagic fever in renal syndrome is characterized by a high degree of sporadicity throughout the year, and the incidence has a significant increase in recent years.
Studies have shown that hemorrhagic fever in renal syndrome has the following epidemiological features:
(1) Male young and middle-aged people are the main pathogenesis of the disease, and most of them are migrant workers, tourism enthusiasts and field workers, and such groups are more likely to be exposed to hemorrhagic fever host animals such as brown rats and haddock rats;
(2) Renal syndrome hemorrhagic fever is a perennial sporadic disease, but it also has seasonal characteristics. The incidence of hemorrhagic fever peaks in autumn and winter, from October to January, and in the spring and summer (March to June), and in mixed-endemic areas, peaks can occur in winter and spring.
(3) Of all the cases, the proportion of patients with rodent activity in the living or working environment is relatively large;
(4) The proportion of patients with typical symptoms is small, among all patients, the elderly are mostly critically ill patients, and the young and middle-aged are mostly mild patients, which may be caused by differences in autoimmune function;
(5) The epidemic situation of renal syndrome hemorrhagic fever of different infectious sources is different, the mouse type is mainly sporadic, and there are epidemics in between, and the incidence of the domestic rat type is more concentrated, which is easy to cause outbreaks or epidemics;
(6) Hemorrhagic fever in renal syndrome is mainly distributed in Asia. In China, northeast China, east China, central south, southwest and other regions are the high incidence areas of the disease.
3. Treatment of hemorrhagic fever in renal syndrome
Patients with hemorrhagic fever in renal syndrome are mainly treated with comprehensive therapy, giving antiviral therapy to early patients and pathophysiology to intermediate and advanced patients. During treatment, patients should be vigilant against sudden shock, renal failure, and bleeding. At present, the treatment of hemorrhagic fever in renal syndrome has the following principles:
(1) Fever period: injection of antiviral drugs, bed rest to reduce extravasation, improve symptoms of poisoning;
(2) Hypotensive shock period: appropriate amount of blood volume supplementation, with acid correction;
(3) Oliguria phase: promote diuresis and diarrhea, stabilize the internal environment;
(4) Polyuria period: maintain the balance of water and electrolytes, pay attention to prevent the occurrence of secondary infections;
(5) Recovery period: ensure adequate nutrition and rest, regularly review renal function, blood pressure and pituitary function, and timely treat abnormal indicators.
2. How is renal syndrome hemorrhagic fever transmitted?
The causative agent of hemorrhagic fever in renal syndrome is hantavirus. In natural cases, hantavirus only causes pathogenesis in humans, and host animals present as latent infections and do not show symptoms of morbidity. Detoxification in infected animals usually begins on the 10th day after infection and lasts for about 30 days, up to a maximum of 120 days.
At present, there are multiple channels of transmission of haemorrhagic fever, and it is believed that there are 3 types of 5 possible transmission routes, namely animal-derived transmission (including through wounds, respiratory tract and digestive tract transmission), mite-borne transmission and vertical transmission, of which animal-derived transmission is the main transmission route. Let's introduce these 5 transmission routes.
(1) Wound transmission: The results of animal tests prove that the rat-infected hantavirus still has an infectious effect in the external environment after being excreted, and a trace amount of blood can be broken through the skin, so that the subject rat is infected, which indicates that it is easier to achieve transmission through the wound. Therefore, the high incidence of people participating in the autumn harvest may be related to skin punctures and an increased chance of infection.
(2) Respiratory transmission: The results of the study prove that hemorrhagic fever can be transmitted through the respiratory tract, especially in the case of dense and large detoxification of poisonous rats indoors (such as animal feeding rooms) or in the wild (such as threshing ground), the aerosols containing viruses formed can be infected by inhalation and even cause epidemics.
(3) Transmission of the digestive tract: Studies have proved that hantavirus can be infected through the digestive tract. Especially in water conservancy sites and camping camps, wild rats are often concentrated in the dormitory, if the prevention work is not done, the food is easily contaminated by the rat excrement, and the eater is infected through the digestive tract.
(4) Mite-borne transmission: Studies have proved that the spread of leather mites and chigger mites among rats and the maintenance of the source of hemorrhagic fever have great significance, and some species may also have a certain role in the transmission of rats.
(5) Vertical transmission: haddock rats, brown rats and rats infected with hantavirus can pass hantavirus to fetal mice, and pregnant women with hemorrhagic fever can also pass hantavirus to fetuses. This vertical transmission, especially in host animals, has implications for the persistence of hantavirus in nature.
3. Symptoms and characteristics of hemorrhagic fever in renal syndrome
Extensive damage of systemic small blood vessels is the main pathological change of hemorrhagic fever in nephrotic syndrome, and the clinical features of the disease are mainly hyperthermia, hypotension, congestive bleeding, and renal damage.
However, patients with renal syndrome haemorrhagic fever generally do not show a clear, specific clinical picture in the early stages. One clinical report showed that up to 67.6% of patients showed only atypical symptoms in the early stages.
Due to this feature, the misdiagnosis and missed diagnosis of hemorrhagic fever in clinical renal syndrome often occur, and the high rate of misdiagnosis and missed diagnosis seriously affects and delays the treatment of patients.
4. How to prevent and control hemorrhagic fever in renal syndrome?
Currently, the main ways to control the prevalence of hemorrhagic fever in renal syndrome are to reduce murine density and to actively vaccinate against renal syndrome hemorrhagic fever.
1. Kill rats and prevent rats
Rat extermination is generally based on the poisoning method, and 2 to 3 times a year to carry out surprise extermination of rats, the time is mainly selected before the hemorrhagic fever epidemic season. Rodents are mainly used with slow-acting rodenticides.
The main method of preventing rats is to do a good job in environmental hygiene, hide food, such as timely removal of garbage, strengthen fecal management; grain and vegetables are raised by more than 0.5 meters and stored away from the wall to remove and reduce the habitat and food sources of rats.
When it is necessary to build a shed for accommodation, the shed should be set up in the shape of a "jie", and the accommodation shed should be covered separately from the kitchen and granary; the bed is elevated. Not less than 0.5 meters from the ground, paving without walls, laying without debris and food; keep the shed dry and rat-free.
2. Mite control and personal protection
In the field operation units such as camping, construction and agricultural reclamation in areas with high incidence of hemorrhagic fever, in the epidemic season of hemorrhagic fever, the mites can be sprayed with 1% dichlorvos solution at 20 to 25 mL/m2 to kill mites.
Field workers should wear shoes, tie cuffs, pants, clothes hanging high, do not sit on grass and grass piles; pay attention to protect the skin, if damaged, timely disinfection and bandaging. Masks should be worn when threshing in threshing.
3. Food management and disinfection of contaminants
Hantavirus is easily inactivated by ultraviolet irradiation, and iodine, ethanol, formalin, lysol, etc. can also inactivate the virus and can be selected as appropriate.
Food hygiene, disinfection of food utensils, food storage work to prevent rat excrement contamination, leftover meals must be fully heated before they can be eaten.
4. Get vaccinated
Since 1994, the mainland has successfully developed three inactivated vaccines against hantavirus, and the epidemiological observation of a large number of people in the epidemic area has proved that the safety, serology and epidemiological effect of these vaccines are good, and the protection rate within 3 years is more than 90%.
When vaccinating, the same type of haemorrhagic fever type should be selected, focusing on high-risk groups in areas with high haemorrhagic fever prevalence.
Boost immunity once a year later with a newly prepared isotype vaccine to increase antibody levels and maintain adequate immunity. It has been reported that within 6 years after basic immunization, the vaccine protection rate for the population is still above 92%. Vaccinations should be completed one month before the start of the peak epidemic season.
In recent years, the mainland has successfully developed a bivalent vaccine for hemorrhagic fever, with 2 doses of basic immunization and 1 injection of strengthening after half a year. Field and laboratory results confirm that it is safe and effective, and can be used in mixed-type epidemic areas and where the nature of the epidemic area is not yet clear.
epilogue
Renal syndrome hemorrhagic fever and its pathogen "hantavirus" is relatively unfamiliar to everyone, but it is a highly contagious and fast-spreading infectious disease with a wide range of continents, with a high incidence and case fatality rate, and the source of infection is the mouse we are familiar with. Therefore, it is still necessary to understand the relevant knowledge of renal syndrome hemorrhagic fever and actively prevent it.
bibliography:
[1] Sun W , Liu Z , Liu Q , et al. Forecast of Hemorrhagic Fever With Renal Syndrome and Meteorological Factors of Three Cities in Liaoning Province, China, 2005–2019[J]. Frontiers in Environmental Science, 2021, 9.
[2] Yang Z , Hu Q , Feng Z , et al. Development and validation of a nomogram for predicting severity in patients with hemorrhagic fever with renal syndrome: A retrospective study[J]. Open Medicine, 2021, 16(1):944-954.
[3] Joao T , Haby M M , Ludovic R , et al. Evidence for Human-to-Human Transmission of Hantavirus: A Systematic Review[J]. The Journal of Infectious Diseases, 2021.