Reovirus
Reovirus is a group of segmented double-stranded RNA viruses belonging to the Reoviridae family.
Reovirus is a icosahedral particle with a diameter of 76 nanometers and a hexagonal shape. It has an inner and outer double-layer core shell surrounding a core with a diameter of 52 nanometers. Core contains 45% RNA. The outer core shell contains 92 concave, cylindrical hollow shell particles, 10 nanometers long, 8 nanometers wide, and a hollow diameter of 4 nanometers.
The chemical composition of reovirus is mainly protein and RNA, and does not contain polysaccharides and lipids. RNA has a double helix structure and can be divided into 10 segments, with a total molecular weight of (14~15)×106. Nucleic acids account for 14% of viral components. 70% of the reovirus protein is the outer nucleocapsid protein, and the rest is the core protein. The core double-stranded RNA does not bind to proteins. The core contains RNA polymerase composed of mRNA transcribed from the parent double-stranded RNA.
Reovirus is highly resistant to heat and general disinfectants. Some virus strains cannot be inactivated even after exposure to 56°C for 2 hours or 70°C for 30 minutes. It can survive for several days under certain conditions and can be stored at -20℃ or -70℃ for several months or one year without losing its infectivity. The virus can survive for at least 1 hour at room temperature in commonly used disinfectants such as 2% Lysol, 3% formaldehyde, 1% phenol solution and 1% peroxide; but in 70% alcohol, it can survive for 1 hour at room temperature. is inactivated. Viruses can be killed by 3% formaldehyde solution at 56°C. Reovirus is resistant to ether, chloroform, sodium deoxycholate, etc., indicating that reovirus does not contain lipids. Reovirus is very stable at a pH value between 2.2 and 8. In a 2 mole MgCl (magnesium chloride) solution, when heated to 50°C, the pathogenicity of the virus is enhanced 4 to 8 times; but when other divalent cations are added, the pathogenicity is not enhanced under the same conditions.
Reovirus can multiply in many different hosts, such as chicken embryo chorioallantoic membrane and allantois. It can proliferate in monkeys, cattle, dogs, guinea pigs, ferrets, hamsters, and suckling rats. It can proliferate well in human and animal tissue culture cells, such as primary cells of humans, monkeys, prairie dogs, cats, pigs, dogs, cattle and sheep. It is also susceptible to HeLa, KB, FL, BSC-1 and other passage cells. Monkey kidney cells are commonly used for virus isolation and titration. After reovirus multiplies in cells, the virus particles are arranged in a lattice shape in the cytoplasm. In addition to complete virus particles, there are also incomplete virus particles and tube-shaped structures. The virus proliferates within the cell and forms Feulgen-negative, RNA-containing intracytoplasmic inclusions around the nucleus. Cytopathies appear slowly, often 10 to 14 days after infection. The typical cytopathic changes of reovirus are different from those of enteroviruses, which are mainly granular changes in cells. If the infection dose is small, the cytopathic effects are difficult to distinguish from non-specific cell degeneration.
All mammalian reoviruses can agglutinate human O-type red blood cells at different temperatures such as 4°C, 25°C, and 37°C. Human reovirus type 3 can also agglutinate bovine red blood cells at 4°C. After bovine red blood cells are treated with receptor-destroying enzyme (RDE), they lose their ability to agglutinate viruses, but human red blood cells are not affected by RDE. The hemagglutinin of reovirus is most stable at 4-37°C and is destroyed at 56°C. Ether does not destroy hemagglutination and does not affect infectivity. Chloroform can destroy hemagglutination but has no effect on infectivity. Because N-2-acylglucosamine can bind to the viral nucleocapsid, it can inhibit hemagglutination.
Reovirus is widespread in humans and animals. Reovirus can often be isolated from healthy children. Reovirus can be isolated from children with fever in winter, children suffering from diarrhea, enteritis, steatorrhea, children suffering from respiratory tract infections, and adults suffering from colds. . In addition, viruses can also be isolated from animals such as orangutans suffering from rhinitis and monkeys suffering from pneumonia. Reovirus was used to infect the nasal cavities of volunteers, resulting in cold-like symptoms and an increase in antibodies. Experimental infections can cause encephalitis or hepatitis in monkeys and colds in orangutans. Infecting suckling mice, the virus invades nerves, myocardium, liver, etc. Infection of pregnant mice results in persistent infection in the fetuses. Experimental infection results show that after infection, although there are large amounts of virus in the lungs and other tissues of animals, and antibodies can also be found in the blood, clinical symptoms may not appear. People infected with reovirus may cause gastrointestinal diseases or mild upper respiratory tract acne, and the clinical symptoms are often not obvious.
If combined with chlamydia, bacterial infection will cause severe clinical symptoms.
Human reoviruses have unique complement fixation antigens. Hemagglutination-inhibiting antibodies and neutralizing antibodies are type-specific. Therefore, neutralization tests and hemagglutination-inhibition tests can distinguish human reovirus types 1, 2, and 3. Type 2 can be divided into subtype 1. The antigenicity of type 1 and type 2 overlaps. Therefore, after being infected with reovirus type 1, in addition to anti-type 1 virus antibodies, the body also has anti-type 2 virus antibodies; similarly, after being infected with reovirus type 2 After infection, antibodies against both type 1 and type 2 viruses increased. However, after infection with reovirus type 3, the body only develops antibodies against type 3 virus.
According to antibody survey results, reovirus is widely present in humans, wild animals, and domestic animals. Toronto conducted an antibody survey on people of different ages and found that the antibodies acquired by babies from their mothers disappear in 3 to 6 months. More than half of 10-year-old children have more than one type of antibody. As age increases, antibodies also increase, and 80% to 100% of adults have more than one type of antibody. After cattle are infected with reovirus, the virus can persist in cow feces for a long time. Therefore, humans can become infected through contact with cows or by drinking milk contaminated with the virus. Reovirus type 3 has also been found in mosquitoes, but there is no evidence that reovirus can cause human infection through insect vectors. Since the virus is easily isolated from feces, it is generally believed that reovirus is infected through the mouth through feces or through the respiratory tract. However, the virus can rarely be isolated from pharyngeal samples. Domestic data proves that the feces of patients or virus carriers contaminate hands, water, food and daily necessities, and oral infection through closer daily contact or drinking water and food is the main mode of transmission. The popular season is mostly in autumn and winter.
The experimental diagnosis method of reovirus is mainly to isolate the virus from the patient's fecal specimens and throat gargle. The patient's urine, blood, and cerebrospinal fluid can also be taken from various organs during autopsy. separation. The most commonly used tissue culture cells are monkey kidney cells, and kidney cells from various animals can be used. Primary human kidney and passage cells such as HeLa, KB, human amniotic membrane, and BSC-1?L cells can also be used. After inoculating the specimen, place it for static culture at 37°C for 21 days, and continue blind passage if necessary. To identify the virus, a complement fixation test is generally used to determine whether it is reovirus, and then a hemagglutination inhibition test or neutralization test is used to determine the type. Immune serum is mostly prepared from rabbits that originally have no natural antibodies. It can also be prepared from guinea pigs and roosters. In addition to virus isolation, serological diagnosis can be performed using a hemagglutination inhibition test.
Rotavirus
Rotavirus is spherical and is a staged double-stranded RNA with a stable structure, heat resistance, acid and alkali resistance, and hemagglutinin on the surface, which inhibits V and When cells come into contact, trypsin can be used to destroy hemagglutinin, making culture more difficult.
After rotavirus enters the human body, it mainly infects small intestinal epithelial cells, causing cell damage and causing diarrhea. At the same time, the villi in the small intestine that help the human body digest are damaged and broken. The small intestine cannot absorb water and nutrients from the human body, and the feces becomes watery after being excreted from the body. Some patients develop dehydration after having diarrhea 10 to 20 times a day during the rotavirus detoxification period. If diarrhea persists, their lives will be further endangered. In addition, complications such as intussusception and convulsions have been discovered in individual patients in recent years.
It takes a week for the villi in the small intestine to repair. Before that, if the child drinks formula, breast milk, milk, or sucrose, the diarrhea may be prolonged.
Autumn diarrhea in infants and young children is a kind of viral infectious diarrhea. According to surveys, 80% to 90% of this type of diarrhea is caused by rotavirus. The virus is spherical when observed under an electron microscope. The middle shell is arranged radially outward like the spokes of a wheel. The outer shell is similar to the outer edge of a wheel. The shape is very similar to a wheel, so it is named rotavirus.
Rotavirus is distributed all over the world. It was prevalent in European and American countries as early as the 1930s. In developing countries such as Asia, Africa, and Latin America, it is the main cause of infant mortality. One of the reasons. Since the 1950s in our country, epidemics have occurred in more than 20 provinces and cities, and its epidemic scope has spread almost throughout the country. This virus has also caused mutual infection in the baby room of the maternity ward, causing diarrhea in many babies and some even causing death.
According to tests, rotavirus will not die for one hour at a high temperature of 50°C; it can survive for 7 years under severe cold conditions of -20°C; and it can survive for a long time in an environment of -70°C. save.
It also has strong tolerance to acids and alkalis. General detergents have no killing effect on it, but it cannot reproduce in the external environment. It is precisely because of these characteristics of the virus that it can lie dormant for a long time in unfavorable environments. Once it has the opportunity to enter the human body, it will multiply and cause disease; then it will be excreted in the feces, pollute the external environment, and re-infect others. This goes on and on, and so far humans have not found an effective drug that can effectively kill the virus.
Although rotavirus is only a small branch in the huge virus family, it also has brothers and sisters. Data show that rotavirus is currently divided into 2 major categories and more than 10 groups. The symptoms caused by each type are basically similar, but the symptoms are slightly different in severity. When the human body is attacked by rotavirus, 2 to 3 days later, the body can produce antibodies against the virus. Generally, within a short period of time, even if you are infected with this virus again, you will not get sick. However, there is no cross-immunity between the various types. That is to say, after being infected with type Ⅰ rotavirus, antibodies to type Ⅰ virus are produced. If you are attacked by type Ⅰ virus again, you may not get sick; but if you are infected with type Ⅰ virus, you will not get sick. Invasion of viruses will still cause disease. Most mothers of newborns have been infected by different rotaviruses. Therefore, the mother's early milk will contain a large number of various types of antibodies. Breast milk, especially colostrum, can provide good protection for newborns. effect.
The main source of infection for rotavirus diarrhea in children is adults or children who shed the virus. After the virus is shed, it often contaminates water sources, food, clothing, toys, appliances, etc. When healthy people come into contact with these items, they will enter the human body through hands and mouth. Animal experiments have also confirmed that viruses can also enter animals through the respiratory tract and cause digestive tract lesions. Whether people can also be infected by rotavirus through the air has not yet been confirmed.
Diarrhea mostly occurs in my country from October to December, accounting for about 80% of the total number of cases. There is also a small peak period from March to May. When infants and young children are infected with rotavirus, the disease begins after an incubation period of 1 to 3 days. The main symptoms in the early stage are vomiting and body temperature between 38 and 39°C, followed by diarrhea. The number of bowel movements is about 10 times a day, and in some children it can be up to 20 times. There may be stool in the early stage. After several bouts of diarrhea, the stool becomes watery or rice soup-like, with no pus and blood and a large amount. Due to a large amount of water loss in children, dehydration occurs quickly, with symptoms such as listlessness, indifferent expression, lethargy, pale complexion, sunken anterior fontanel and eye sockets, loose skin that cannot be flattened immediately after pinching, oliguria, and dry oral mucosa. , if dehydration is not corrected in time, it can often lead to death. It is not difficult for doctors or experienced parents to make a correct diagnosis based on the characteristics of the season, water samples, and absence of pus and blood. The key is whether they can receive correct and timely treatment.
At present, there is no specific drug to kill rotavirus, and various antibacterial drugs currently used are ineffective against the virus. The correct treatment method is to correct the child's dehydration and acidosis as soon as possible. Children with mild symptoms can be corrected with oral rehydration. Oral rehydration salts recommended by the World Health Organization are commonly used (the formula is: 3.5 grams of sodium chloride, 2.5 grams of sodium bicarbonate, 1.5 grams of potassium chloride, 20 grams of glucose plus 1000 ml of water), which can allow children to Drink as water. Children with severe symptoms can use intravenous infusion to correct dehydration and acidosis, along with oral administration of dipyridamole. It is reported that dipyridamole has a significant inhibitory effect on rotavirus. In recent years, interferon has also been used to treat rotavirus infection. This drug can inhibit the reproduction of the virus in the human body, thereby reducing symptoms and shortening the course of the disease.
In addition, oral rehydration solutions are constantly improving. Earlier, rice soup was used to replace glucose oral liquid in Southeast Asia and achieved good results. Some people in our country have used fried rice or millet to make rice soup and take it orally instead of liquid medicine, and achieved obvious results. The specific preparation method is: fry the rice or millet over low heat until brown, then add water to make a gruel, filter to remove the rice grains, and feed the rice soup to the children. The fried rice grains have been partially carbonized and have the effect of adsorbing toxins and stopping diarrhea. You can also add burnt rice soup instead of water to the oral liquid recommended by the World Health Organization for your children to drink. If there is no oral rehydration agent, you can add 3.5 grams of salt, 2 grams of baking soda, and 30 grams of sugar to every 1000 ml of burnt rice soup. The starch, vitamins and other minerals in rice water can not only supplement the child's nutrition, but also help restore the child's gastrointestinal function. It is currently an ideal treatment method.
If a newborn has autumn diarrhea, he or she should continue to feed breast milk or colostrum. About 90% of breast milk or colostrum contains anti-rotavirus antibodies, which can alleviate symptoms or shorten the course of the disease.
In recent years, great progress has been made in the prevention of autumn diarrhea. In addition to following the general prevention methods of intestinal infectious diseases, such as isolating patients, washing hands before meals and after using the toilet, and not eating unwashed or spoiled food. Outside of food. There are reports that vaccinating pregnant women with rotavirus vaccine can increase rotavirus antibodies in breast milk, and newborns who eat this kind of breast milk can improve their ability to resist rotavirus infection. In addition, oral rotavirus vaccine is considered to be the most effective and simple prevention method. Currently, many countries are conducting research, and some have produced live attenuated human rotavirus vaccines and passaged live attenuated rotavirus vaccines. Bovine or monkey rotavirus vaccines and live attenuated recombinant vaccines. Some vaccines have been clinically tested and have not caused adverse reactions in adults or infants. Some countries are using recombinant DNA technology to develop a rotavirus vaccine. It is expected that in the near future, this vaccine will be widely promoted and used around the world, just like the oral administration of jellyfish pills.