Prevention of Influenza

Vaccination

Annual vaccination is the main and most effective way to prevent influenza and influenza-related complications, especially for high-risk groups.Influenza vaccines are trivalent or quadrivalent and provide protection against H1N1 strains, H3N2 strains, and one or both IBV strains corresponding to the two IBV lineages.There are two types of vaccines in use: inactivated vaccines that contain "killed" (i.e. inactivated) virus, and live attenuated influenza vaccines (LAIV) that contain weakened virus.Inactivated vaccines are divided into three types: whole virus, split virus (in which the virus is destroyed by a detergent), and subunit (containing only the viral antigens HA and NA).Most influenza vaccines are inactivated and administered intramuscularly. LAIV is sprayed into the nose.Vaccination recommendations vary by country.Some countries recommend vaccination for all persons over a certain age, such as 6 months,while other countries' recommendations are limited to high-risk groups, such as pregnant women, young children (excluding newborns), the elderly, people with chronic diseases conditions, health care workers,people in contact with high-risk populations, and people who can easily spread the virus.Young infants cannot be vaccinated against influenza for safety reasons, but they can inherit passive immunity from their mother if she received the inactivated vaccine during pregnancy.Influenza vaccination also helps reduce the likelihood of genetic recombination.

In general, flu vaccines are only effective if there is an antigenic match between the vaccine strain and the circulating strain.Furthermore, most commercially available influenza vaccines are produced by propagating influenza virus in embryonated eggs, which takes 6–8 months.Influenza seasons differ between the northern and southern hemispheres,so WHO meets twice a year, one in each hemisphere, to discuss which strains should be included in influenza vaccines based on observations from HA suppression tests.Other manufacturing methods include inactivated vaccines based on MDCK cell culture and recombinant subunit vaccines produced by overexpression of baculovirus in insect cells.

Antiviral chemoprophylaxis

Post-exposure prophylaxis can prevent or reduce the severity of influenza, with the antiviral drug oseltamivir given by mouth to children at least three months old and zanamivir inhaled by children over seven years old.Chemoprophylaxis is most useful in groups at high risk of complications and in those who cannot receive influenza vaccination because of contraindications or lack of effectiveness.Postexposure chemoprophylaxis is only recommended when oseltamivir is administered within 48 hours of exposure to a confirmed or suspected case of influenza and zanamivir is administered within 36 hours.It is recommended that it be offered to people who have not been vaccinated for the current flu season, who have been vaccinated less than two weeks after exposure, if there is a significant mismatch between the vaccine and the circulating strain, or during an influenza outbreak Closed environment regardless of vaccination history.

Infection control

Hand hygiene is important to reduce the spread of flu.This includes washing your hands often with soap and water, using an alcohol-based hand sanitizer, and keeping your hands away from your eyes, nose, and mouth.It is important to cover your mouth and nose when you cough or sneeze.Other ways to limit the spread of influenza include staying home when sick,avoiding contact with others for a day until symptoms end, [9] and disinfecting surfaces that may be contaminated with the virus, such as doorknobs.Health education is often carried out through the media and posters to remind people to pay attention to the above etiquette and hygiene.There is uncertainty about the use of face masks, as studies to date have not shown that use of face masks significantly reduces seasonal influenza.Likewise, the effectiveness of point-of-entry screening across countries has not been well studied.Social distancing measures such as closing schools, avoiding contact with infected people through isolation or quarantine, and limiting mass gatherings may reduce transmission,but these measures are often costly, unpopular, and difficult to implement.Therefore, commonly recommended infection control methods are respiratory etiquette, hand hygiene, and mask wearing, which are inexpensive and easy to implement. Drug measures are effective but may not be available in the early stages of an outbreak.

In healthcare settings, infected people may be grouped or assigned to separate rooms.If there is a risk of exposure to infected body fluids, it is recommended to wear protective clothing such as masks, gloves and gowns when in contact with infected persons.Keeping the patient in a negative pressure room and avoiding aerosol-generating activities may be helpful,but special air handling and ventilation systems are not considered necessary to prevent airborne transmission of influenza.In residential settings, new admissions may need to be closed until the spread of influenza is controlled.When sending a patient to a nursing home, it is important to be aware of any known outbreaks of influenza.Because influenza viruses circulate in animals such as birds and pigs, it is important to prevent transmission from these animals.Water treatment, keeping animals indoors, quarantining sick animals, vaccination and biosecurity are the main measures used.Placing poultry and swine houses on elevated ground away from high-density farms, backyard farms, live bird markets, and water can help minimize contact with wild birds.Closure of live poultry markets appears to be the most effective measure and has been shown to be effective in controlling the spread of H5N1, H7N9 and H9N2.Other biosecurity measures include cleaning and disinfecting facilities and vehicles, prohibiting visits to poultry farms, not bringing poultry back to the farm for slaughter,changing clothes, disinfecting footbaths, and disposing of food and water.

If live poultry markets are not closed, influenza viruses can be reduced with a "clean-up day" (i.e., unsold poultry is removed and the facility is sanitized) and a "no carryover" policy that eliminates infectious material before new poultry arrives Spread. If a novel influenza virus violates the above biosecurity measures, rapid detection through isolation, decontamination, and culling may be necessary to eradicate it to prevent the virus from becoming endemic.Vaccines for avian subtypes H5, H7 and H9 exist in some countries.For example, in China, vaccination of poultry against H7N9 successfully limited its spread, suggesting that vaccination may be an effective strategy if used in combination with other measures to limit spread.In pigs and horses, the management of influenza depends on biosafety vaccination.