What is the flu?


The flu is an extremely common illness. Regardless of age, all people may be affected by the flu. Generally, the flu is more common in winter, although it can be detected all the year round. That’s why experts recommend people to get a flu shot in mid-October. In some tropical regions, the illness tends to be associated with the rainy reason.

The causative agent of the flu is the influenza virus. There are three types of flu viruses: A, B, and C. Influenza A viruses are the most common type in humans, but influenza B and C viruses also cause seasonal or local epidemics. Influenza A viruses can be divided into many different subtypes according to the viral surface proteins hemagglutinin (HA) and neuraminidase (NA). So far, many different HA and NA molecules have been identified. Each virus has one type of HA and one type of NA. Have you ever heard of H1N1, H3N2, or H7N9? Through the introduction above, it’s now easy to understand that H7N9 virus refers to an influenza A virus that possesses an HA 7 protein and an NA 9 protein.

Transmission of the flu

Influenza virus can be easily transmitted from person-to-person, either through directly contacting with an infected person, contacting with contaminated objects, or inhaling aerosols or small droplets containing influenza viruses. Scientists think that influenza viruses are mainly spread via small droplets made by infected people. When an infected person coughs, sneezes or talks, a large number of virus particles are spread to the air through small droplets.

Symptoms of the flu and differences between the flu and a cold

Signs and symptoms of the flu are similar to those of a cold but are generally worse. Common symptoms of the flu include fever, cough, chills, sweats, fatigue, weakness, headache, sore throat, runny or stuffy nose, muscle or body aches, vomiting, and diarrhea. Most people getting the flu have no or only mild symptoms that only last several days and do not need treatment. But some affected people may develop severe illness that can lead to hospitalization and even death.

Although the flu and the common cold are both respiratory illnesses and have some similar symptoms, they are not the same things. First of all, the two illnesses are caused by different viruses. As mentioned above, the flu is caused by influenza viruses. The common cold, however, is caused by over 200 different kinds of viruses, particularly rhinoviruses (30-80%) and coronaviruses (15%). Second, the common cold almost does not cause serious health problems, whereas the flu may cause severe complications like pneumonia, myocarditis, encephalitis, sinus problems, ear infections, multi-organ failure, and worsening of chronic medical conditions like asthma and diabetes. Recent evidence suggests that the flu kills more globally than previously thought. At present, it is estimated that 290,000 to 650,000 deaths are associated with respiratory diseases and severe complications induced by the flu each year.

Who are at a high risk for the flu?

  1. Children under the age of 5
  2. Old people aged 65 or above
  3. Pregnant women
  4. People who have certain medical conditions or receive treatments that affect their immune systems
  5. People living in long-term care facilities like nursing homes and rehabilitation and retirement centers

These populations of people tend to have weakened immune systems compared with the general population, making them susceptible to the flu and related complications. It’s well known that the immune system is a host defense system against various pathogens. If this defense system is weakened or impaired, the body will be less likely to fight off influenza viruses.

The immune system can also be affected by smoking, alcohol consumption, poor nutrition, lack of sleep, and other unhealthy lifestyles. Therefore, people who have an unhealthy lifestyle are also at a higher risk for the flu. In addition, being in crowded places such as in schools, college dormitories, and office buildings also increases your risk of getting the flu. This is determined by the transmission means of influenza viruses.

How to prevent flu?

Scientists studying influenza viruses are responsible for developing novel flu vaccines each year. Getting a flu shot is an important strategy to protect yourself from the flu. But flu vaccines are not 100% effective. The major reason is that influenza viruses mutate quickly and there are many different subtypes of influenza viruses. A particular flu vaccine generally only protects against some but not all influenza virus strains. It’s difficult for scientists to predict which subtypes will circulate in the upcoming flu season, and it’s also difficult to develop broad-spectrum flu vaccines. These are why we need new flu vaccines each year.

Although getting vaccinated is an important strategy for flu prevention, it is not suitable for all people. Infants younger than 6 months and individuals allergic to flu vaccines generally are not recommended to get a flu shot.

Moreover, there are many other things that you can do to reduce the risk for the flu, such as washing your hands frequently, not touching your face, not going to crowded places, getting enough sleep, and getting regular exercise. Well, living a healthy life is always a method to reduce the risk of various diseases.

Recent research on influenza viruses

At present, there are no treatments that can cure the flu. Medications are available to reduce the course of the illness, such as oseltamivir, amantadine, zanamivir, and rimantadine. Scientists have been studying the interactions between influenza viruses and host cells for years, in a hope to find more effective therapeutic agents and broad-spectrum vaccines. A recent study suggests that lactic acid bacteria (LAB) may provide broad protection against influenza viruses. Such research would help us address the big health issue.

In summary, the flu is a common illness in humans and still killing large numbers of people annually. The prevention of the flu is not simply the work of scientists and governments. To protect ourselves from the flu, we need to know more about it and improve our self-protection consciousness.

Author bio

Caroline Liu is an editor at Cusabio Biotech Co., Ltd, a company with ten years of experience in manufacture and research of life sciences reagents, such as proteins, antibodies, and ELISA kits.

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