Influenza A viruses, the culprits of respiratory illness in humans, are a complex and multifaceted group of viruses. Among the numerous subtypes of Influenza A, H1N1 and H3N2 with a notorious history of causing seasonal epidemics and pandemics, demand special attention.
Figure 1. The Spread of Influenza A.
Influenza A H1N1, also known as the swine flu, is a formidable subtype of Influenza A virus that made its first appearance in pigs in 1930. Its ominous presence resulted in a pandemic in 2009, and the World Health Organization (WHO) declared it a public health emergency of international concern. The pandemic’s spread was unprecedented, reaching numerous countries and causing a significant impact on morbidity and mortality. In the first year alone, the H1N1 pandemic claimed between 151,700 and 575,400 lives.
The H1N1 virus, a type A virus in the Orthomyxoviridae family, harbors a segmented RNA genome that codes for 11 proteins. The H protein is responsible for the virus’s ability to infect host cells, while the N protein helps the virus spread from cell to cell. The virus spreads through respiratory droplets and can survive on surfaces for a few hours. It has a short incubation period of 1-4 days, and the symptoms manifest suddenly.
The symptoms of H1N1 bear similarity to those of other influenza types, including fever, cough, sore throat, body aches, headache, chills, and fatigue. Gastrointestinal symptoms such as diarrhea and vomiting may also occur. Although most people recover without complications, vulnerable populations, such as young children, pregnant women, and those with underlying health conditions, are at a heightened risk of severe illness and death.
To combat the H1N1 virus, treatment usually involves antiviral medications, such as oseltamivir (Tamiflu) or zanamivir (Relenza). If started early, these drugs can decrease the severity and duration of the illness.
Influenza A H3N2, another subtype of Influenza A virus, is a seasonal epidemic trigger. The virus first made its appearance in humans in 1968 and has caused several pandemics since then. H3N2, another type A virus in the Orthomyxoviridae family, also has a segmented RNA genome that codes for 11 proteins. This subtype has been known to cause more severe illness than H1N1 and has been around for many years.
H3N2 manifests symptoms similar to those of other influenza types, including fever, cough, sore throat, body aches, headache, chills, and fatigue. Gastrointestinal symptoms may also appear in some individuals. Although most people recover without complications, some are at a heightened risk of severe illness and death.
Treatment for H3N2 follows a similar approach to that of H1N1. Antiviral medications such as oseltamivir (Tamiflu) or zanamivir (Relenza) are the go-to drugs. In severe cases, supportive care such as oxygen therapy and mechanical ventilation may be necessary.
Prevention is the most effective way to steer clear of Influenza A viruses such as H1N1 and H3N2. Getting vaccinated every year is the most potent preventive measure. The flu vaccine is engineered to protect against the influenza strains that are likely to circulate during the upcoming season. Other preventive measures include washing hands frequently, avoiding close contact with sick people, covering the mouth and nose when coughing or sneezing, and staying home when sick.