Seasonal influenza is an acute respiratory infection caused by influenza viruses. It is common in all parts of the world. There are 4 types of influenza viruses, types A, B, C and D. Influenza A and B viruses circulate and cause seasonal epidemics of disease.
1) Influenza A viruses are further classified into subtypes according to the combinations of the proteins on the surface of the virus. Currently circulating in humans are subtype A(H1N1) and A(H3N2) influenza viruses. The A(H1N1) is also written as A(H1N1)pdm09 as it caused the pandemic in 2009 and replaced the previous A(H1N1) virus which had circulated prior to 2009. Only influenza type A viruses are known to have caused pandemics.
2) Influenza B viruses are not classified into subtypes but can be broken down into lineages. Influenza type B viruses belong to either B/Yamagata or B/Victoria lineage.
3) Influenza C virus is detected less frequently and usually causes mild infections, thus does not present public health importance.
4) Influenza D viruses primarily affect cattle and are not known to infect or cause illness in people.
Symptoms of influenza usually begin around 2 days after being infected by someone who has the virus such as cough, headache, and sore throat. The cough can be severe and can last 2 weeks or more. Most people recover from fever and other symptoms within a week without requiring medical attention. However, influenza can cause severe illness or death, especially in people at high risk. Influenza can worsen symptoms of other chronic diseases. In severe cases influenza can lead to pneumonia and sepsis. People with other medical issues or who have severe symptoms should seek medical care. Hospitalization and death due to influenza occur mainly among high-risk groups.
Seasonal influenza spreads easily, with rapid transmission in crowded areas including schools and nursing homes. When an infected person coughs or sneezes, droplets containing viruses are dispersed into the air and can infect persons in close proximity. The virus can also be spread by hands contaminated with influenza viruses. To prevent transmission, people should cover their mouth and nose with a tissue when coughing and wash their hands regularly. In temperate climates, seasonal epidemics occur mainly during winter, while in tropical regions, influenza may occur throughout the year, causing outbreaks more irregularly. The time from infection to illness, known as the incubation period, is about 2 days, but ranges from 1–4 days.
Vaccination is the best way to prevent influenza. Safe and effective vaccines have been used for more than 60 years. Immunity from vaccination goes away over time so annual vaccination is recommended to protect against influenza.
In Thailand between October 2024 and January 2025, 39.46% of flu cases were attributed to A/H1N1 (pdm09), while 34.86% were linked to B (Victoria) and 25.68% to A (H3N2). A total of 107,570 influenza cases have been recorded in Thailand in 2025, and nine people have died of the virus. The 10 provinces with the highest infection rates per 100,000 people are Phayao (638.55), Lamphun (591.61), Chiang Rai (469.88), Phuket (456.36), Chiang Mai (443.04), Lampang (374.70), Nan (341.83), Bangkok (331.85), Ubon Ratchathani (301.93), and Nonthaburi (290.59).
Because of the severe situation, a Thai herb is conducted in a hope to fight against the influenza A (H1N1) which is spreading more widely. The Traditional Thai and Alternative Medicine Development Department and Chiang Mai University have worked together in a joint study on Plu kaow. Its fermented could effectively act against the viruses and bacteria. It could also build the immune system against diseases.
Plu kaow (Houttuynia cordata Thunb.) is a perennial plant that belongs to the ‘Saururaceae’ family. It is widely found in East Asia and is commonly used as a vegetable in local cuisine. It has been used for centuries as a folk medicine and is also utilized in the preparation of fermented beverages, nutraceuticals, feed, and cosmetics. It is rich in various nutrients such as protein, soluble sugar, fat, volatile oils, total flavonoids, and trace elements like sulfur (S), phosphorus (P), potassium (K), magnesium (Mg), calcium (Ca), iron (Fe), zinc (Zn), and copper (Cu).
Moreover, there are a lot of important compositions including volatile oils, flavonoids, and phenolic compound. Volatile oils have a broad range of pharmacological activities, including antimicrobial, antiallergic, antimutagenic, enzyme inhibiting, insecticidal, antiviral, and neurodegenerative effects. Flavonoids have the ability to modulate the activity of stimuli and affect the functions of various cellular structures, indicating that they may have important antiosteoporotic, antihepatotoxic, antiallergic, antitumor, and anti-inflammatory properties. Phenolic has potential as an anticarcinogenic and antigenotoxic agent, and catechin, which has hypolipidemic, immunomodulatory, and antiproliferative properties.
References:
1) https://www.who.int
2) https://www.nationthailand.com
3) https://mgronline.com
4) https://www.apecinterlab.com
5) Pradhan S., Rituparna S., Dehury H., Dhall M., and Sing Y.D. (2023) Nutritional profile and pharmacological aspect of Houttuynia cordata Thunb. and their therapeutic applications, Pharmacological Research – Modern Chinese Medicine (9), 100311.
