pathogen

Seasonal influenza (flu) is an acute respiratory disease caused by influenza virus. In Hong Kong, influenza is generally more prevalent in January to March and July to August. There are three known types of influenza viruses: A, B, and C. Influenza A virus can be subdivided into different subtypes according to the two antigen types of hemagglutinin (H) and neuraminidase (N) on the surface of the virus. Currently, there are two subtypes of seasonal influenza A virus circulating in humans, A(H1N1)pdm09 and A(H3N2). In the spring of 2009, the influenza A(H1N1)pdm09 virus first emerged and caused isolated cases of human infection, leading to an influenza pandemic in mid-2009. Influenza A(H1N1)pdm09 virus is now one of the seasonal influenza strains worldwide.

The emergence of seasonal influenza virus antigenic drift (slight changes) produces new strains. New strains of the influenza virus arise from time to time, and irregularly. Therefore, the World Health Organization recommends each year the flu vaccine mix that should be used during the flu season.
Seasonal flu is not the same as a pandemic flu. A virus strain capable of causing a pandemic occurs when a novel influenza virus undergoes an antigenic shift (significant change) that allows it to be transmitted efficiently from person to person. Humans have limited or no resistance to this virus, allowing the new virus to spread faster and more widely than seasonal flu.

Influenza pandemics have occurred about every 10-50 years in the past. However, the timing of future influenza pandemics cannot be predicted. Influenza pandemics are usually accompanied by more infections and more severe illnesses, leading to higher mortality rates and significant social and economic impacts.

way for spreading

Healthy people usually recover on their own within two to seven days after contracting seasonal influenza. Symptoms include fever, cough, sore throat, runny nose, muscle pain, fatigue and headache; vomiting and diarrhea may also occur.

Cough is usually severe and lasts for a long time, but fever and other symptoms usually subside within five to seven days. However, if people with weakened immunity or the elderly are infected with influenza, it can be a serious illness, and complications such as bronchitis or pneumonia may occur, and even death.

Symptoms

Influenza virus is mainly transmitted through droplets produced when the sick person coughs, sneezes or talks, and can also be spread through direct contact with the secretions of the sick person.

incubation period

Generally about one to four days.

contagious period

Patients can infect others from about one day before onset to five to seven days after onset. In young children or those who are severely immunocompromised, the infectious period can be even longer.

Governance method

Get plenty of rest and drink plenty of fluids.

Do not go to work or school if you have flu-like symptoms. If symptoms persist or worsen, seek medical advice immediately.

Antibiotics are medicines that treat bacterial infections, not viral infections. Taking antibiotics will not cure flu or speed up recovery.

Antiviral agents can alleviate the condition and shorten the duration of the illness, but they must be taken with a doctor's prescription.

prevention method

Seasonal Flu Vaccination

Vaccines are safe and effective in preventing seasonal influenza and its complications.

Influenza can cause serious illness in high-risk individuals and can affect healthy individuals. Based on the safety and effectiveness of seasonal influenza vaccines, except those with known contraindications, all persons aged 6 months or above should receive influenza vaccines to protect their personal health.

It is generally recommended to get the flu vaccine every autumn. About two weeks after the vaccination, the body will produce enough antibodies to fight against the flu.

*For more information on seasonal flu vaccines, see Vaccination Schedule.

Personal and Environmental Hygiene

Wash your hands frequently with liquid soap and water, especially before touching your mouth, nose or eyes, or after touching public facilities such as handrails or doorknobs.

When hands are not visibly soiled, it is also effective to clean hands with 70% - 80% alcohol-based handrub.

Cover your mouth and nose when you sneeze or cough, and wash your hands thoroughly afterwards.

Dispose of soiled tissues in a covered trash can.

Surgical masks should be worn in case of respiratory infection symptoms.

Keep indoor air circulating.

During peak flu season, avoid going to crowded or poorly ventilated public places; high-risk individuals may consider wearing a surgical mask when staying in these places.

Maintain a balanced diet, regular exercise and adequate rest, do not smoke and avoid excessive life stress.