Mexico is still in the third wave of the coronavirus and a new seasonal influenza season is approaching. The seasonal influenza season usually begins in late September and ends in April, although it usually extends into May. Last year, the 2020-2021 seasonal influenza season began in week 40 and ended in week 20 of 2021.

What is influenza?

According to the Pan American Health Organization (PAHO), influenza is a viral infection that mainly affects the nose, throat, bronchial tubes, and, occasionally, the lungs. The infection usually lasts one week and is characterized by the sudden onset of high fever, muscle aches, headache, severe malaise, dry cough, sore throat, and rhinitis.

The virus is easily transmitted from person to person by droplets and small particles expelled by coughing or sneezing. Influenza usually spreads rapidly in the form of seasonal epidemics. There are four types of seasonal influenza viruses: A, B, C, and D. Type A and B influenza viruses cause seasonal epidemics.

Influenza A viruses are classified into subtypes based on combinations of two surface proteins: hemagglutinin (HA) and neuraminidase (NA). The subtypes currently circulating in humans are A(H1N1) and A(H3N2). A(H1N1) is also known as A(H1N1)pdm09, as it caused the 2009 pandemic and subsequently replaced the seasonal influenza A(H1N1) virus circulating until then. All known pandemics have been caused by influenza A viruses. Type B viruses are not classified into subtypes, but the currently circulating viruses can be divided into two lineages B/Yamagata and B/Victoria.

Infection usually lasts one week and is characterized by the sudden onset of high fever, muscle aches, headache, severe malaise, dry cough, sore throat, and rhinitis.

How is influenza transmitted?

Influenza is transmitted from person to person (the virus enters the body through the mouth, nose, and eyes), through droplets of saliva that are expelled when sneezing or coughing; also when shaking hands, kissing, or hugging a person sick with a respiratory infection.

You can also become infected by having contact with surfaces previously contaminated by saliva droplets from a person sick with influenza, such as tables, computer keyboards, sports equipment, handles, railings, telephones, tissues, and fabrics, according to the Mexican Institute of Social Security (IMSS).

Influenza Symptoms

Since 2020, confusion over the symptoms of COVID-19 and influenza is common, as they share some of the same symptoms. Influenza symptoms are:

Fever above 38°C, cough, and headache.
Runny nose
Nasal redness
Nasal congestion
Joint pain
Muscle pain
Decay (prostration)
Pain on swallowing
Chest pain
Stomach pain
Diarrhea