Influenza is an acute infectious disease that affects the respiratory tract. It is characterized by the abrupt onset of headache, fevers, chills, muscle pains, severe malaise, cough, sore throat and rhinitis. The acute illness generally resolves over three to five days, and most patients largely recover within a week or two without medical treatment. However, the disease can be severe in very young children, the elderly and patients with serious medical conditions. The infection can lead to severe complications such as pneumonia and even death.
Contact with Infected People
The World Health Organization states that the influenza virus is commonly spread from person to person through droplets and small particles produced when infected patients sneeze or cough. The incubation period is about 18 to 72 hours. Some common characteristics of the onset of influenza infection include high fever, coughing and body aches. Influenza can spread quickly during seasonal epidemics, which often occur in the late fall and early winter.
Influenza Virus Types
According to the Clinton County Government of Pennsylvania Pandemic Information, influenza type A, B and C are the three main types of influenza-causing viruses. Influenza A virus can infect animals as well as humans. Infected animals will serve as hosts for the virus, which then can be transmitted to other animals and humans. There are several subtypes of influenza under type A influenza virus. Influenza B and C are found only in humans, and these cause fewer epidemics than influenza type A. Influenza type C is the mildest form.
Weak Immune System
A weak immune system allows more viruses to enter and infect the body. According to the University of South Carolina School of Medicine, the influenza virus is usually most severe in children under age 6 and in the elderly. Youngsters have not yet built up antibodies and elderly people may be in frail health.
