Facing this summer's flu, how to "know yourself and know the enemy" to avoid being infected

Recently, the positive rate of influenza testing in some southern provinces has continued to rise, and Fujian, Guangdong, Hainan, Jiangxi and other places have issued emergency warnings one after another. According to the weekly influenza situation summary of the National Influenza Center, the epidemic intensity of influenza this summer has increased significantly compared with the same period in the past two years. At the same time, influenza activity in northern provinces of my country is at an extremely low level.

Why does this wave of flu favor the south in summer so much?

How to differentiate influenza virus infection and new coronavirus infection through symptoms?

In the face of influenza, how can we remain invincible without being humble or arrogant?

Let's hear from the experts.

Why is there a high incidence of influenza in the south during summer?

This flu is mainly "type A3", that is, A (H3N2) subtype influenza virus. The prevalence of influenza is closely related to the geographical location and the subtype of influenza. According to the "Technical Guidelines for Influenza Vaccination in China (2021-2022)" issued by the Chinese Center for Disease Control and Prevention, the annual periodicity of influenza A (type A) in my country increases with latitude, and presents diverse spatial patterns and seasonal characteristics: northern provinces north of 33 degrees north latitude show a winter epidemic pattern, with a single annual peak from January to February each year; southern provinces south of 27 degrees north latitude show a single annual peak from April to June each year; the mid-latitude regions between the two show a double cycle peak from January to February and from June to August each year. Influenza B (type B) is highly prevalent in a single winter in most parts of my country.

The influenza virus A(H3N2) subtype prevalent in southern provinces this year also conforms to the phenomenon of a single annual peak from April to June in southern provinces south of 27 degrees north latitude. At the same time, the double cycle peak in mid-latitude regions also includes June to August. This is why the influenza this summer is mostly rampant in the south, while the north is relatively safe.

Are children the main targets?

The flu has caused pediatric departments in many hospitals to be overcrowded. Therefore, many people believe that the main targets of the flu are children, and speculate that this is related to the fact that children spend too much time at home in a simple and clean environment, which leads to a decrease in their immunity.

In fact, the general population is susceptible to influenza viruses. According to statistics from the Shenzhen Center for Disease Control and Prevention, 48% of the influenza patients were children aged 0 to 14, less than half. The influenza infection rate is affected by many factors, but the simple and clean home environment will not increase the infection rate.

The main reason for the above misconception is that children (especially school-age children) live in childcare institutions and schools, which are crowded places, which are conducive to the spread of diseases and prone to clustered cases. At the same time, after children are infected with influenza viruses, the detoxification time may exceed one week (the virus generally continues to be detoxified in human respiratory secretions for 3 to 7 days), which also increases the chance of influenza transmission.

Children are usually active and have more contact with others, objects and environmental surfaces, but they generally cannot consciously maintain good hand hygiene. In addition, children's immune systems are not yet fully developed and are susceptible to respiratory infections. These factors do increase the probability of children being infected with the influenza virus.

How to quickly identify if you have the flu

According to the "Influenza Diagnosis and Treatment Program (2020 Edition)", the main symptoms of influenza are fever, headache, myalgia and general discomfort. The body temperature can reach 39℃～40℃, with chills and chills, often accompanied by systemic symptoms such as muscle and joint pain, fatigue, and loss of appetite. There are often sore throats and dry coughs. There may be local symptoms such as nasal congestion, runny nose, discomfort behind the sternum, facial flushing, and conjunctival congestion. Some patients have mild symptoms or no flu symptoms. Children infected with influenza B often have vomiting, abdominal pain, and diarrhea as the main manifestations. Those without complications are self-limiting, and the fever gradually subsides 3 to 4 days after the onset of the disease, and the systemic symptoms improve, but coughing and physical recovery often take a long time.

Although the prominent manifestations of influenza are fever, headache, and myalgia, these symptoms can also be seen in other viral infections such as the new coronavirus. It is difficult for the public to accurately identify influenza based on symptoms alone. The epidemiological history plus symptoms can help identify influenza early. There are corresponding epidemiological histories after influenza virus infection and new coronavirus infection. Influenza patients often come into contact with other influenza patients before they become ill, or there are clusters of influenza cases in the patient's work, study, or living environment.

If you have flu-like symptoms, you need to seek medical attention immediately. Doctors make a diagnosis based on epidemiological history, clinical manifestations, and etiological tests. The most intuitive basis is viral antigen detection and viral nucleic acid detection.

Virus antigen testing is done by collecting blood samples for testing. The results are fast, but the sensitivity is low, far lower than nucleic acid testing. If the antigen test result is positive, the patient can be diagnosed with influenza, but if the result is negative, influenza virus infection cannot be ruled out. Virus nucleic acid testing is done through respiratory specimens (nasal swabs, throat swabs, nasopharyngeal or tracheal extracts, sputum), with high sensitivity and specificity, and can distinguish between virus types and subtypes. H1N1 and H3N2 are completed through this test.

What to do after infection

After confirming that you have been infected with the influenza virus, do not panic or feel anxious. A small number of patients will need to be hospitalized for complications, but most infected people will recover within a week.

Flu treatment includes antiviral treatment, symptomatic treatment (such as fever reduction), and treatment of complications. Some types of influenza viruses have targeted antiviral drugs (such as oseltamivir), and antiviral treatment usually lasts for 5 days. Antiviral treatment is not required in all cases, and drugs have a certain incidence of adverse reactions and should be used under the guidance of a doctor. Doctors will use different treatment plans according to the severity of the disease.

After being infected with the virus, you should pay attention to avoid cross-infection among family members. This requires isolating the infected person as much as possible (such as living in a separate room, not eating with other family members, etc.), doing a good job of daily cleaning and disinfection, washing hands frequently, and improving ventilation.

There are ways to prevent the flu

Flu vaccination is one of the most effective ways to prevent influenza that has been scientifically proven. It is recommended that people aged 6 months and above who are willing to receive the flu vaccine and have no contraindications can make an appointment for flu vaccination, especially key groups such as the elderly, children, pregnant women, patients with chronic diseases, family members and caregivers of infants under 6 months old.

So if I get the flu shot right now, tomorrow, will it be effective in preventing the flu this summer?

It takes about 14 days for the flu vaccine to produce antibodies. If you haven't received the flu vaccine yet, it is recommended that you get it as soon as possible. It is generally recommended to get the flu vaccine from September to November each year, because this period of time can better cover the prevention of flu in the winter, spring and summer of the following year.

In addition, to prevent influenza, you should pay attention to the following details:

☆ Keep the environment ventilated. If you need to close the doors and windows due to weather conditions, you can open the windows for ventilation at regular intervals. It is recommended that the ventilation time should not be less than 30 minutes each time.

☆ During the peak influenza season, try to avoid crowded and enclosed places. If you are in crowded places or around people with flu-like symptoms, you should wear a mask that can prevent droplets (such as disposable medical masks), and the mask should cover both the nose and mouth.

☆ Develop good personal hygiene habits. Wash your hands frequently, avoid touching your eyes (such as rubbing your eyes), nose (such as picking your nose) and mouth (such as picking your teeth), pay attention to cough etiquette (bend your upper arm to cover your mouth and nose with your upper arm or tissue when coughing or sneezing), and avoid covering your mouth with your hands, because it is common to forget to wash your hands after covering them.

☆ Ensure adequate sleep, avoid anxiety, eat a healthy diet, have a balanced diet, increase exercise, and enhance your own resistance.

author:

Zong Zhiyong, Infectious Disease Center, West China Hospital, Sichuan University

Wang Yantong, Hospital Infection Management Department

Review: Experts from the National Health Science Expert Database

Department of Respiratory and Critical Care Medicine, West China Hospital, Sichuan University

Chief Physician Liang Zongan

Planning: Wu Weihong, Tan Jia

Editor: Luan Zhaolin