As flu season arrives, here’s what parents need to know…

Flu, learn about it!

Influenza (flu for short) is an acute respiratory infectious disease caused by influenza virus, which is divided into four types: A, B, C, and D. The most common type of influenza is seasonal influenza, which occurs in autumn and winter and is mainly caused by influenza A and B viruses.

Flu in children often develops suddenly, with the main symptom being fever, with the highest body temperature reaching 39-40°C, often accompanied by chills and shivering. Children may also experience headaches, muscle aches, fatigue, loss of appetite, and other symptoms of a cold. There may also be symptoms of a cold such as cough, sore throat, runny nose, and nasal congestion, and a small number may have digestive tract manifestations, such as nausea, vomiting, diarrhea, and so on. The symptoms of flu in infants and young children are often not as typical as those in children, and may only manifest as fever and cough. Flu in newborns is relatively rare, but complications often occur, such as pneumonia and difficulty breathing.

Mild influenza often presents similarly to the common cold, but with more obvious fever and systemic symptoms. Severely ill children may experience viral pneumonia, secondary bacterial pneumonia, acute respiratory distress syndrome, shock, disseminated intravascular coagulation, cardiovascular and nervous system extrapulmonary manifestations, and multiple complications. Severe influenza and fatal cases often occur in people with chronic underlying diseases, especially children under 5 years old, and especially infants under 1 year old.

Influenza patients and asymptomatic carriers are the main sources of seasonal influenza infection, which is mainly transmitted through droplets of respiratory secretions, and can also be transmitted through direct or indirect contact with mucous membranes such as the mouth, nose, and eyes.

Due to the variable genes of influenza viruses and the diverse biological characteristics of their hosts, new mutant strains continue to emerge, so they can spread widely among the population, causing repeated infections and illness. On January 22, 2020, Netflix launched a documentary "Pandemic: How to Prevent a Flu Pandemic". The documentary begins with an introduction to the Spanish flu in 1918, which quickly swept across Europe, Asia, and North America within 18 months, killing tens of millions of people and becoming the largest infectious disease disaster in human history. The documentary tells a frustrating fact that too many people are "ignorantly optimistic" in the face of the epidemic. It warns everyone that the next flu pandemic is not about whether it will happen, but when it will happen. So everyone must pay attention and do their best to prevent it for their children and family members. A flu outbreak is really terrifying.

Influenza "Killer"-Neuraminidase Inhibitor

Unlike the common cold, influenza has its own "nemesis", which is the neuraminidase inhibitor. Currently, those on the market in China include oseltamivir, zanamivir and peramivir.

Oseltamivir is an oral preparation. my country's State Food and Drug Administration (CFDA) has approved oseltamivir for the treatment of influenza A and B in adults and children aged ≥1 year, and for the prevention of influenza A and B in adults and adolescents aged ≥13 years. The U.S. Food and Drug Administration (FDA) has approved it for use in children over two weeks of age. Zanamivir is an inhaled powder spray that can be used for children over 7 years old. The guidelines recommend that zanamivir can be used for inhaled treatment when oseltamivir is not available or cannot be used, or when patients are seriously ill. Peramivir is an intravenous injection and is suitable for critically ill patients who cannot take it orally or are resistant to oseltamivir. Due to the oral dosage form of oseltamivir, it is more convenient to use and is more commonly used at home. Let's mainly introduce oseltamivir below.

Oseltamivir is currently the most widely used anti-influenza virus drug for adults and children. Oseltamivir is available in two dosage forms: granules (15 mg and 25 mg) and capsules (75 mg). The best time to administer is within 48 hours of the onset of influenza symptoms, and administration after 96 hours of symptoms is also effective. For specific therapeutic and preventive doses, please refer to Table 1.

Table 1 Therapeutic and preventive doses of oseltamivir

Although vaccination is the best way to prevent influenza virus infection, during an influenza outbreak, people who cannot be vaccinated and the following key children are recommended to take oseltamivir for prevention.

Recommended drug prevention population:

High-risk children who cannot receive influenza vaccine, or children with immune abnormalities who do not respond to the vaccine.

High-risk children within 2 weeks of vaccination.

With unimmunized high-risk children or age