What is the relationship between cold and flu？ Does the flu vaccine have side effects？ The experts have come to dispel doubts.

　　The flu season is coming again. It is estimated that about 10% to 20% people will get the flu every year. National Health Commission recently issued a reminder that the influenza virus has become increasingly active since the end of this month, reminding the public to do a good job in disease prevention. What is the relationship between cold and flu? What is an influenza-like case? Do you want to get the flu vaccine? Is it useful to get the flu vaccine? Listen to Professor Wang Yuedan from Peking University School of Basic Medicine.

　　The difference between cold and flu.

　　Everyone may catch a "cold" every year, even more than once. For ordinary patients, the symptoms of a cold seem to be similar, and it is difficult to find out whether they are suffering from a cold or flu. Are colds classified and how are they classified?

　　Wang Yuedan: A cold refers to an upper respiratory infection. It can be divided into viral cold (such as upper respiratory tract infection caused by influenza virus, adenovirus and rhinovirus) and bacterial cold (such as bacterial pharyngeal tonsillitis). Among them, viral colds are mostly caused by rhinovirus, parainfluenza virus (not the same as influenza virus), respiratory syncytial virus, echovirus, Coxsackie virus, coronavirus and adenovirus. The clinical symptoms are nasal congestion, sneezing, runny nose, fever, cough, headache, etc., which are mostly self-limiting. Although it occurs frequently in winter and spring, there will be no pandemic.

　　Influenza refers to influenza, which is an acute respiratory infectious disease caused by influenza virus (influenza for short), and it is also a highly contagious and fast-spreading disease. It is mainly spread through droplets in the air, contact between people or contact with contaminated items. Typical clinical symptoms are: sudden high fever, general pain, obvious fatigue and mild respiratory symptoms.

　　Influenza patients and recessive infected people (some people infected with influenza virus may have no symptoms and become recessive infected people, which is not easy to be found. However, these recessive infected people can also emit viruses through saliva droplets, which is the main source of influenza infection, and it is contagious from the end of latent period to the acute period.

　　"Influenza-like cases" cannot be ignored.

　　In epidemic reporting, people often see a word "flu-like cases". What does this mean?

　　Wang Yuedan: In many cases, many flu patients are not diagnosed because of the lack of timely medical treatment and laboratory evidence. For example, in the report on the epidemic situation of legal infectious diseases published by China in 2018, the number of reported cases of influenza was 765,186, and the incidence rate was only 55.0851 per 100,000 (equivalent to 0.055%), far below the predicted value of 10%.

　　On the other hand, there are many other pathogens, such as respiratory syncytial virus, coronavirus and mycoplasma, which can also cause flu-like symptoms. If there is no clear evidence of etiology or serological diagnosis, it is difficult to differentiate from the flu only in clinical manifestations, and the consequences of its infection are similar to those of the flu. In some people, it can also cause severe infection or secondary bacterial infection, and even lead to the death of patients. It is also an acute infectious disease that needs vigilance.

　　Therefore, the disease control departments and medical institutions in China will have fever (axillary temperature ≥ 38℃), accompanied by one of the symptoms of cough or sore throat, the diseases that lack the basis of laboratory diagnosis are collectively referred to as influenza-like cases, and are reported and monitored in the "China Influenza Monitoring Information System" and the "Public Health Emergencies Management Information System". In some cities of our country, there is an explosive epidemic of influenza-like cases every year, which seriously threatens people’s healthy life. At present, the main pathogens causing influenza-like cases in China include influenza virus, parainfluenza virus, respiratory syncytial virus, coronavirus, rotavirus, adenovirus, human metapneumovirus, mycoplasma, chlamydia and Legionella.

　　Influenza has seasons.

　　Is the flu seasonal?

　　Wang Yuedan: The epidemic of influenza and influenza-like cases has obvious seasonality, which is closely related to weather phenomena such as temperature changes, but it has different seasonal characteristics in different regions of China. For example, in northern areas such as Beijing and Qinghai, influenza is mainly prevalent in winter and spring; Shenzhen and other southern regions are mainly popular in July and August; However, the influenza epidemic in Shanghai presents a double peak cycle pattern from January to February and from July to August.

　　Influenza is preventable, controllable and treatable.

　　Can influenza be prevented?

　　Wang Yuedan: If proper preventive measures are taken, the flu can be prevented and controlled. Specific measures include: controlling and avoiding contact with the source of infection, timely treatment, reporting and isolation of influenza patients,

　　Don’t go to crowded places during the flu season; To cut off the route of infectious diseases, you can wear masks and goggles. In key areas and places (such as hospitals and stations), you should ensure air circulation and do a good job in disinfection of the environment. Protect susceptible people, strengthen physical exercise at ordinary times, and improve the body’s physique and resistance to diseases; In extreme weather such as rapid temperature drop, we should pay attention to keep warm and not give the flu virus an opportunity. For the elderly, frail or high-risk people (such as medical staff in fever clinics in hospitals), influenza vaccine can be vaccinated for protection.

　　How to treat the flu?

　　Wang Yuedan: For viral colds, pay attention to rest, warmth and nutrition, and deal with symptoms (for example, high fever can reduce fever). Most people can heal themselves. Antibiotics can be used to treat bacterial colds. But no matter what kind of cold, if the symptoms persist or show signs of deterioration, patients should seek medical attention in time.

　　Do you want to get the flu vaccine?

　　What is the flu vaccine? Is there a difference between the flu vaccine for the elderly, adults and children?

　　Wang Yuedan: Influenza vaccine is used to prevent influenza caused by influenza virus. At present, many countries, including China, mainly use inactivated influenza virus vaccine, which is generally composed of three inactivated virus components or four inactivated virus components, called trivalent vaccine and tetravalent vaccine respectively.

　　Why is there a difference between trivalent and tetravalent influenza vaccine? This is because influenza A virus is easy to mutate, while influenza B virus is less variable, so the general trivalent seasonal influenza vaccine is not aimed at all influenza B viruses. However, in many cities in China, seasonal influenza often accounts for a large proportion, so it will also produce tetravalent vaccines that can resist more types of influenza B virus.

　　At present, there is no influenza vaccine specifically for the elderly, adults and children, and the vaccine components of all age groups are the same.

　　Can influenza vaccination effectively prevent influenza?

　　Wang Yuedan: After vaccination, it usually takes 2-3 weeks to develop immunity to the corresponding serotype of influenza virus, but just like drugs, influenza vaccine can only ensure that most people (generally more than 85%) can produce protective immunity, but even if a few people are vaccinated with influenza vaccine, they will still be infected by the corresponding type of influenza virus. When there is a big variation of influenza virus, the immunity generated by influenza vaccine may be ineffective. At this time, it is necessary to follow the guidelines of the disease control department, regardless of whether the general seasonal influenza vaccine has been vaccinated in that year, it is necessary to vaccinate the influenza vaccine against the mutant strain.

　　Generally speaking, after being vaccinated with influenza vaccine, people who are infected with influenza virus of the same serotype or serotype with cross-immune protection will have less symptoms even if they have influenza.

　　Does the flu vaccine have side effects?

　　Wang Yuedan: Like other vaccines, flu vaccination may cause symptoms such as local swelling and pain, fatigue discomfort or fever, but these symptoms are generally mild, and they can be relieved and cured by themselves even if they are not treated. Compared with the serious consequences caused by influenza, the side effects of influenza vaccination can be ignored, so it is unwise to refuse influenza vaccination for fear of side effects.

　　interlinkage

　　Experts stressed:

　　Influenza is a common respiratory infectious disease that seriously threatens human health, and it is also a preventable, controllable and treatable disease. It can not only be vaccinated with influenza, but also be prevented and controlled in all directions by avoiding contact with influenza patients or recessive infected people, wearing masks and taking necessary air environment disinfection measures. For the vast majority of people, there is no need to panic and worry too much about getting the flu, nor should we take it lightly to avoid severe flu or secondary bacterial infection. To this end, we should do three things, that is, keep warm, rest and supplement nutrition, so that the general symptoms can be cured by themselves or after treatment. If you do the above three things correctly and the flu symptoms still persist or show signs of aggravation, you should seek medical treatment in time.