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Influenza is now widespread in 49 states in the United States and it has already claimed the lives of 37 children since October last year, according to the Centers for Disease Control and Prevention. While the immune system can fight off the infection, influenza has a serious capability to kill a person in several ways if left untreated.
Invasion of the Respiratory System
The influenza virus usually enters the host through the eyes, nose or mouth and attacks the cells in the nose and throat to multiply. With a massive amount of viral particles in the body, the immune system responds by sending troops composed of white blood cells, antibodies, and inflammatory molecules to eliminate the invaders. In most cases, a healthy adult recovers from influenza within days or weeks.
However, some situations are unfavorable wherein the immune system causes a new problem. The high load of viral particles in the respiratory system can trigger the immune system to overproduce inflammatory molecules. Too much of these molecules can destroy lung tissues, impairing their ability to deliver oxygen to the blood. The result is hypoxia or lack of oxygen in the bloodstream and death. This is the primary killing ability of the influenza virus.
Exhausting the Immune System
While the immune system is occupied with the influenza infection, other pathogenic agents like bacteria can take their opportunity to start an invasion. The most common complication of influenza is pneumonia, considered a secondary infection caused by bacteria. Both Streptococcus and Staphylococcus bacteria can infect the lungs that result in pneumonia, the inflammation of air sacs inside the lungs. The stress from both influenza and pneumonia makes breathing extremely difficult in addition to other symptoms, such as body aches, weakness, and chest pain.
"Flu is a deadly infectious disease that kills thousands of people every year,” said Dr. Amesh Adalja, an infectious disease specialist at the Center for Health Security at the University of Pittsburgh Medical Center.
Spread from Lungs to other Body Parts
Since the immune system is dealing with influenza, the bacterial infection in the respiratory system can spread to the other parts of the body through the bloodstream. It triggers an inflammatory response from the immune system delivered through the bloodstream. The effect damages many organ systems that usually leads to multiple organ failure. The phenomenon is called septicemia or sepsis.
In sepsis, the person can feel the specific signs, such as shivering, extreme discomfort or pain, pale skin color or skin discoloration, confusion or drowsiness, shortness of breath, and the feeling of dying. In physiology, the body undergoes numerous changes including fever, rapid breathing, elevated heart rate, edema or swelling, high blood sugar, and low blood pressure.
Sepsis is a time-based health condition, requiring immediate medical attention. Administration of two antibiotics – aerobic and aerobic – must be performed without delay to counter the bacterial infection. A severe case of sepsis requires broad-spectrum antibiotics to cover a wider variety of bacteria. Other management methods include intravenous fluids to correct electrolyte imbalance and blood products to replace blood loss due to acute hemorrhage or severe hypoxemia.
Inflammation of the Brain, Heart, and Muscle Tissues
Influenza viral particles can also trigger inflammation of the brain, the heart, and muscle tissues, which are considered severe complications from the original infection:
- When the virus attacks the brain, it causes inflammation of the organ or encephalitis. Influenza-associated encephalitis is a rare complication of the viral infection. It is not fully understood yet, but scientists associate the role of immune response in triggering encephalitis.
- When the virus attacks the heart, it causes inflammation of the blood-pumping organ or myocarditis. Acute myocarditis associated with influenza virus is a rare complication that can occur in children. It can lead to cardiac arrest, heart impairment, and heart failure.
- The virus can also attack muscle tissues that may trigger viral myositis. It is a rare condition that has been reported as a result of the attack of viruses such as influenza A and B, and the Epstein-Barr virus.
- If the virus attacks the skeletal muscles, the damage can lead to rhabdomyolysis, a serious clinical complication leading to skeletal muscle death.
The progression of influenza depends on the person’s environment, the strength and stability of the immune system, and the existence of any underlying health condition. People with chronic illnesses, such as diabetes or renal problems, with compromised immune system caused by HIV or cancer, and those with premature or weakened immune system like children and the elderly, are at risk of influenza-related complications.
Globally, the influenza virus can cause 3 to 5 million cases of severe infection and 291,000 to 646,000 deaths every year, according to the CDC and the World Health Organization. To date, the flu vaccine is still considered as the best protection against the virus.
"The flu vaccine is a very safe vaccine that saves lives. Studies have shown that of the children who died from the flu in the US last year, 85 percent were not immunized,” said Dr. Claire Bocchini, an infectious disease specialist at Texas Children’s Hospital.
[메디컬리포트=Ralph Chen 기자]