How to prevent and control influenza in the spring season

Author: Zhang Chaofan, chief nurse in the Department of Infectious Diseases at Peking Union Medical College Hospital. Review: Zhou Baotong, Associate Chief Physician of the Infectious Diseases Department at Peking Union Medical College Hospital.

Title: How to prevent and control influenza in the spring season.

Introduction: Influenza is highly contagious. Vaccination and good hygiene reduce infection risk, especially for the elderly and those with chronic illnesses.

Keywords: ['Influenza', 'Prevention']

During the periods of the Beginning of Spring and Rain Water, the climate is very changeable and there is an increase in population movement and gatherings, marking a peak season for influenza outbreaks. Understanding and implementing effective flu prevention and control measures is crucial for protecting one's health and that of one's family.

1. What is influenza?

Influenza, commonly referred to as the flu, is an acute febrile respiratory infectious disease caused by the influenza virus, transmitted through respiratory droplets. Patients usually experience a sudden onset of symptoms such as chills, high fever, headache, fatigue, general muscle aches, and respiratory issues.

Human influenza viruses are categorized into three types: A, B, and C. Among them, type A influenza viruses frequently mutate, posing a risk of pandemics; type B influenza viruses typically cause localized outbreaks and are not associated with pandemics; type C influenza viruses are seen in sporadic outbreaks, particularly in children.

Is the flu the same as a common cold?

Influenza is not to be confused with a common cold: Common colds can be caused by various viruses, such as rhinoviruses and coronaviruses, primarily manifesting upper respiratory symptoms like nasal congestion, runny nose, and sore throat, with little to no systemic symptoms such as fever, and are generally less contagious.

Influenza is specifically caused by the influenza virus. Although it may begin with upper respiratory symptoms, most patients experience a sudden onset of high fever, chills, headache, and significant fatigue, alongside other systemic symptoms. The virus has high contagiousness and spreads quickly. Typically, the illness duration is short and often self-limiting. However, elderly individuals and those with chronic respiratory diseases, heart conditions, or compromised immune systems may develop influenza virus pneumonia, myocarditis, or secondary bacterial infections, which can be life-threatening.

The flu spreads through several methods.

The influenza virus primarily spreads through airborne droplets. The virus is present in the respiratory secretions of infected individuals or asymptomatic carriers and is released into the environment through actions like speaking, coughing, or sneezing. The virus can remain airborne for up to 30 minutes, making it easy for susceptible individuals to become infected upon inhaling.

Sources of infection include patients and asymptomatic carriers (some infected individuals do not display symptoms). Animals such as poultry and pigs can also transmit the avian influenza virus to humans under specific circumstances.

After the onset of illness, patients can expel the virus through secretions like nasal mucus, saliva, and phlegm. The infectious period typically lasts about one week, peaking in transmissibility 2 to 3 days after symptom onset.

4. How is influenza diagnosed?

If symptoms typical of a common cold, such as sore throat, runny nose, and nasal congestion, rapidly escalate into high fever, body aches, and fatigue, one should suspect influenza. This is particularly important if similar cases arise among close contacts such as family members, colleagues, or classmates. It is advisable to visit a hospital's fever clinic for assessment. Doctors can diagnose influenza by collecting a nasopharyngeal swab for rapid testing of influenza virus antigens or nucleic acids.

5. How to treat influenza?

After influenza onset, treatment should be comprehensive: provide basic supportive care and management of symptoms to relieve discomfort. Antiviral medications should be chosen based on medical advice, and taking these medications within 48 hours of flu symptom onset is most effective. This can alleviate flu symptoms and reduce the duration of illness by 1 to 3 days, potentially helping to lower complications and reduce hospitalization rates.

The primary antiviral drugs for influenza currently include Oseltamivir and Baloxavir. Oseltamivir, an older medication, is used for treating and preventing influenza types A and B in individuals aged one year and older, requiring several days of continuous use. Conversely, Baloxavir is a newer antiviral suitable for treating influenza types A and B in individuals aged five years and above, administered as a single dose. However, its efficacy and safety in children under five years remain unclear, and it is not currently recommended for preventive use.

6. How to prevent influenza during peak season?

In our country, receiving the influenza vaccine from September to November each year is an effective strategy to prevent influenza, significantly reducing the risk for vaccine recipients to contract the illness and experience severe complications.

Daily protective measures can effectively reduce the infection and spread of influenza, including: maintaining good respiratory hygiene by covering your mouth and nose with a tissue or towel when sneezing or coughing; washing hands frequently and avoiding touching the face; consuming a balanced diet, exercising moderately, and ensuring adequate rest; avoiding close contact with individuals showing flu-like symptoms; and minimizing visits to crowded places during the flu season.

How long is the flu vaccine effective after vaccination?

Antibodies appear about one week after infection or vaccination with the influenza virus vaccine, peak at 2 to 3 weeks, and begin to decline after 1 to 2 months, dropping to lower levels around one year. There is no cross-immunity among different types and subtypes of the influenza virus. Additionally, because the influenza A virus can mutate easily and the vaccine is designed based on previously circulating strains, its effectiveness may vary. Nonetheless, overall, it can still decrease incidence and lessen the severity of the disease.

8. Who is the flu vaccine suitable for?

Currently available influenza vaccines include inactivated whole virus vaccines, split vaccines, and subunit vaccines. The vaccines predominantly used in our country consist of split vaccines and subunit vaccines, which are considered non-pathogenic and have good safety profiles.

All individuals aged 6 months and older without contraindications to vaccination should receive the influenza vaccine. Prioritization is recommended for the following key high-risk groups for timely vaccination:

Medical staff, such as clinical treatment personnel, public health workers, and health quarantine staff;

Elderly individuals aged 65 and older;

Individuals with one or more chronic diseases;

Vulnerable populations and staff in congregate settings such as nursing homes, long-term care facilities, and welfare institutions;

Pregnant women;

Children aged 6 to 59 months;

Family members and caregivers of infants under six months old;

Key populations in childcare institutions, primary and secondary schools, and regulatory sites.

References:

Wang Jiyao, Ge Junbo, Zou Hejian. Practical Internal Medicine (Volume 1) [M]. Beijing: People’s Medical Publishing House, 2022, 3: 247-251.

Wang Yuming, Li Mengdong. Practical Infectious Diseases [M]. Beijing: People's Health Publishing House, 2016: 439-443.