H3N2 Influenza Virus Pathogenesis, Transmission and Complications: A Narrative Review

The recent outbreak of the influenza virus has grown to be a significant issue and a matter of great concern in terms of controlling the impending influenza pandemic. The influenza virus poses a serious threat as it directly infects and impairs the immune system reaction and the respiratory tract. The virus effectively produces infectious viral particles when haemagglutinin molecules are properly cleaved at the respiratory epithelium. The mode of transmission is via droplets from an affected case. The lungs, responsible for the vital exchange of gases, can fail due to various mechanisms, including the destruction of epithelial cells, significant degradation of the extracellular matrix, and airway obstruction. Influenza is a primary cause of severe pneumonia, but it can be accompanied by further bacterial infections, commonly involving bacteria such as Streptococcus pneumoniae and S. aureus. Influenza infection increases the susceptibility to developing Acute Respiratory Distress Syndrome (ARDS) and bacterial sepsis. Both adults and children have a 30-50% chance of experiencing viral infections along with bacterial pneumonia. Notably, Influenza A virus (H3N2) influenza has been associated with a significant increase in admissions to intensive care units. Among the factors contributing to the development of ARDS, individuals between the ages of 36 and 55 years, pregnant women, and obese individuals are at a higher risk. However, infection with influenza viruses A (H3N2) or B, female sex, and influenza vaccination have been identified as protective factors against ARDS. Influenza infection increases the susceptibility to developing ARDS and bacterial sepsis. Disease progression can be limited by spreading awareness among the people about the factors responsible for transmission, clinical manifestations, and preventive methodologies.