Dengue fever

Dengue:

Dengue virus infection can cause recessive infection, dengue fever, dengue hemorrhagic fever, and dengue hemorrhagic fever is rare in my country. The typical clinical manifestations of dengue fever include sudden onset, high fever, headache, severe muscle and bone and joint pain, skin rashes, bleeding tendency, lymphadenopathy, decreased white blood cell count, and thrombocytopenia in some patients. Guangdong, Hong Kong, Macau and other places in my country are dengue fever endemic areas. Since the disease is transmitted by the Aedes mosquito, the epidemic has a certain seasonality, usually from May to November each year, with a peak in July to September. In the new epidemic area, the population is generally susceptible, but the disease is mainly in adults, and in the endemic area, the disease is mainly in children.

Cause:

Dengue virus belongs to the flavivirus genus in the Flaviviridae family. It is a single-stranded positive-stranded RNA virus. The virus is resistant to low temperature. It can survive for 5 years at -20°C and more than 8 years at -70°C, but it is not resistant. Heat, 50 ℃ 30 minutes or 100 ℃ 2 minutes can be inactivated, not acid resistant, use detergent, ether, ultraviolet light and 0.65% formaldehyde solution can be inactivated. At present, 4 serotypes of dengue virus have been isolated, all of which are pathogenic. Aedes mosquitoes (including Aedes aegypti and Aedes albopictus) are the main hosts, and patients and recessive infections are the main sources of infection. The patient is most contagious from 1 day after the onset of the disease to 3 days after the onset of the disease. A small number of patients can also isolate the virus from the blood on the 3rd day after the fever has subsided.

Dengue virus enters the human body through the bite of the Aedes mosquito, and enters the blood circulation after the capillary endothelial cell and mononuclear-phagocyte system proliferate, forming the first toxemia. Then it is located in the mononuclear-phagocytic cell system and lymphatic tissue to replicate, and is released into the blood again to form a second toxemia. Dengue virus and the anti-dengue virus antibodies produced by the body form an immune complex, which activates the complement system, leading to increased vascular permeability. At the same time, the virus can inhibit the bone marrow, leading to white blood cell, thrombocytopenia and bleeding tendency.

Clinical manifestations:

The incubation period is 3 to 14 days, with an average of 4 to 7 days. Clinically, dengue fever is divided into typical, mild and severe.

1. Typical Dengue Fever:

(1) The onset of fever is mostly sudden, and the body temperature quickly reaches above 39°C, usually lasting for 2 to 7 days. The fever is often irregular. In some cases, the body temperature drops to normal on the 3rd to 5th day, and then rises again after 1 day. Bimodal heat or saddle heat. Child cases have a slower onset and lower fever. It is accompanied by headache, back pain, muscle and joint pain, orbital pain, and post-eye pain and other systemic symptoms. There may be gastrointestinal symptoms such as hyperesthesia, nausea, vomiting, abdominal pain, poor appetite, diarrhea and constipation. Congestion of the face and conjunctiva, flushing of the neck and upper chest skin. Relative slow pulse may appear during the fever period.

(2) The rash appears 2 to 5 days after the onset of the disease. It is first seen on the palms, soles of the feet or torso and abdomen, and gradually extends to the neck and limbs. Some patients are seen on the face. It can be maculopapular rash, measles-like rash, scarlet fever-like rash, erythema , Slightly irritating, and also in the last day of fever or after the fever subsides, small ecchymosis appears on the feet, back of legs, ankles, back of wrists, armpits, etc., which subside within 1 to 3 days, leaving brown spots temporarily, generally with The body temperature subsided at the same time.

(3) Bleeding 5 to 8 days after the onset of the disease, about half of the cases may have different parts and different degrees of bleeding, such as epistaxis, skin petechia, gastrointestinal bleeding, hemoptysis, hematuria, vaginal bleeding, etc.

(4) Others There may be slight swelling of lymph nodes throughout the body with light tenderness. Hepatomegaly may be present, but splenomegaly is rare. Individual cases have jaundice. After the illness, patients often feel weak and weak, and it usually takes several weeks to fully recover.

 Dengue fever

2. Light Dengue Fever:

Symptoms and signs are milder than typical dengue fever, fever and body pain are mild, rash is rare or not going to the doctor, there is no bleeding tendency, and the superficial lymph nodes are often swollen. Its clinical manifestations are similar to influenza, which is easy to be ignored and healed in 1 to 4 days.

3. Severe dengue fever:

The patient’s early manifestations were similar to typical dengue fever. On the 3rd to 5th day of the course of the disease, the condition suddenly worsened, with severe headache, nausea, vomiting, disturbance of consciousness, and neck stiffness and other meningitis manifestations. Some manifested as massive gastrointestinal bleeding and hemorrhagic shock. This type is often due to rapid development of the disease, mostly due to central respiratory failure and hemorrhagic shock, death within 24 hours.

An examination:

1. Routine inspection:

(1) The total number of white blood cells in patients with dengue fever in the peripheral blood decreases at the onset of the disease, especially in the rash stage; the percentage of neutrophils is also reduced, and the lymphocytes are relatively increased, and poisoning particles and obvious nucleus shifting to the left are seen, which are abnormal. Lymphocytes, the blood picture returned to normal 1 week after fever. Thrombocytopenia in 1/4 to 3/4 cases can be as low as 13×109/L.

(2) Urine routine may have a small amount of protein, red blood cells, white blood cells, and sometimes casts.

2. Virus isolation:

 

Take blood from early patients, inoculate it in Aedes albopictus cell strain (C6/36), and isolate the virus to be identified by specific neutralization test or hemagglutination inhibition test.

3. Serum immunological examination:

ELISA is used to detect specific IgM antibodies in the patient's serum, and the positive is helpful for the early diagnosis of dengue fever. If dengue virus antigen is detected in the patient's serum, it can also be used as a basis for a clear diagnosis.

4. Dengue fever virus nucleic acid detection:

The detection of dengue virus RNA in the serum of patients is more sensitive than virus isolation, and can be used for early rapid diagnosis and serotype identification, but the technical requirements are higher.

2. Lower body temperature:

For patients with high fever, it is advisable to use physical cooling, such as ice compress, alcohol bath, and cautious use of analgesic and antipyretic drugs. For those with persistent high fever and severe toxic blood symptoms, short-term use of small doses of adrenal cortex hormones, such as oral prednisone, can be used.

3. Rehydration:

For those with excessive sweating and diarrhea, take oral rehydration first, and pay attention to the balance of water, electrolytes and acid-base. When necessary, intravenous fluids should be used to correct dehydration, hypokalemia and metabolic acidosis, but we should always be alert to the possibility of inducing cerebral edema, intracranial hypertension, and cerebral herniation.

4. Reduce intracranial pressure:

For severe headache and intracranial hypertension, 20% mannitol injection should be used for rapid intravenous drip in time. At the same time, intravenous drip of dexamethasone can help reduce cerebral edema and reduce intracranial pressure. For patients whose respiratory center is inhibited, artificial ventilator should be used for treatment in time.

5. Hemostasis:

Those with bleeding tendency should be given general hemostatic drugs such as carbachol and vitamin K. Whole blood or platelets can be transfused when the amount of bleeding is large.

Prognosis:

Dengue fever is an infectious disease with self-limiting tendency, and the course of disease is about 10 days for patients without complications. The disease usually has a good prognosis. Most of the deaths were severe patients.

prevention:

1. Manage the source of infection:

Endemic areas or areas likely to be endemic should do a good job of monitoring and forecasting dengue fever epidemics, early detection, early diagnosis, and timely isolation and treatment. Specific laboratory tests should be performed as soon as possible to identify mild patients. Suspicious patients should be medically observed, and the patients should be isolated in a hospital room with screened windows and doors, and the isolation time should be no less than 5 days. Strengthen frontier health and quarantine.

2. Cut off the route of transmission:

Preventing mosquitoes and killing mosquitoes are the fundamental measures to prevent this disease. Improve the sanitation environment, eliminate breeding grounds for Aedes mosquitoes, and clean up stagnant water. Spray mosquitoes to destroy adult mosquitoes.

3. Protect susceptible people:

Improve the population's disease resistance, pay attention to a balanced diet, work and rest, proper exercise, and enhance physical fitness. During the epidemic, apply insect repellent to susceptible people to prevent mosquito bites.

Detect infection:

In March 2019, the University of Bath in the United Kingdom announced that researchers at the school are developing a small device to detect dengue virus infection earlier, so that patients can be treated more efficiently and avoid deterioration. The team believes that a better understanding of how these cells behave after infection can find a more precise way to detect dengue virus .

Epidemic:

According to news on September 17, 2021, India has suffered the worst dengue fever in decades, which has caused hundreds of deaths.