Changing weather from cooler climates to spring season, and then summer and autumn are always welcome, but usually spells the onset of flu season. In India, acute respiratory illness (ARI) forms a huge health burden of illness. Let us know what is influenza, what are its symptoms, how does it spread and how to prevent flu.
Flu and flu like illnesses are characterised by fever with or without chills, sore throat, common cold, malaise and cough. It spreads fast and very easily via secretions or droplet transmission.
It is of particular importance to note that it spreads rapidly in crowded environments like schools and nursing homes. If the infected person sneezes or coughs, the virus can spread upto 1 metre easily. It also spreads by contaminated hands. Usually the incubation period (exposure to disease ) is 2 days, but it can be anywhere from 2-4 days .
What causes flu?
Flu is mostly caused by influenza viruses which are of 4 main types – ABCD. Type A and type B are of particular importance. There are other virus like rhino virus, respiratory syncytial virus that can also cause flu like illness but the common form is influenza. The virus can easily mutate and hence changes itself every year. The World Health Organization (WHO) convenes every year in February and October to determine the virulence of the strain and ascertain the circulating types.
The most common perception about influenza is that it is a regular cold and it shall pass. While that is true, the disease can range from mild to severe. Elderly, children upto 5 years, individuals on steroids or other immunosuppressive therapy, with long-term lung conditions, as well as pregnant women are at a higher risk.
No one can predict who lands up with a complicated lung illness. The cough due to a bout of influenza can last upto 2 weeks.
Also read: Fever isn’t always flu! 7 conditions which may seem like flu, but aren’t
Is there a way to prevent influenza?
There is no permanent immunity to influenza, either with natural infection or vaccination due to the changing nature of the virus. But the vaccination can prevent infection with the circulating strain of virus. Several outbreaks in history have been due to influenza like SARS1, H1N1 epidemic etc, have been noted.
Vaccination is recommended to everyone above the age of 6 months. WHO has a list of recommendations for children, pregnant women, individuals with chronic medical conditions, healthcare workers, hosteliers, military personnel and even people going for pilgrimage.
Through worldwide surveillance , WHO announces its strain of virus for the next batch of vaccines in February for northern strain and September for southern strain. These strains are incorporated by various vaccine companies when being formulated.
How to prevent influence
1. Go for annual vaccination
2. If suffering from illness, it is best to stay home and avoid work or school.
3. Stay hydrated.
4. Take anti-fever medications as prescribed and some decongestants as suggested by the doctor.
5. Monitor for deteriorating symptoms – breathlessness, hacking cough and dehydration.
All about the influenza vaccine
An annual dose of influenza vaccine is recommended for all high risk groups and even normal population. The peak season for India is monsoon. The best timing for vaccination to avoid this peak is April-May.
The second peak is in November-February, mostly winter in northern states. In India, WHO recommends SH strain of vaccine starting from April. If no data about previous influenza vaccine is available or while vaccinating for the first time, 2 doses are recommended.
There are 2 kinds of vaccines: Trivalent, which includes 2 types of influenza and 1 strain of influenza B, and Quadrivalent, which includes 2 strains of both influenza type A and type B. Both are effective.
Are there any side effects to the influenza vaccine?
Like any other vaccination, it may cause a mild fever or running nose for a day or two. Some people report an achy limb where the vaccine is given. This vaccine has been in use for more than 50 years in the world.
Are there people who shouldn’t take the vaccine?
People with severe documented egg allergy must not take the egg based culture vaccines. People suffering from an acute episode of asthma or on immune suppressant therapy should not be given the live attenuated influenza vaccines.
What is the impact of Covid-19 on influenza activity?
The influenza seasonality dipped sharply in 2020 due to high safety strategies which included masking, hand hygiene, travel restrictions and isolation. In fact, experts suggested Covid-19 and influenza could be combated with vaccine. As per 2022 surveillance data, we are back to pre-pandemic levels.
Influenza while being a mild illness most of the time, is a cause of significant morbidity and loss of productivity, including school or work absenteeism.
It is unpredictable in its virulence and its aggressive nature. Hence, prevention with vaccination is better than cure.