Days are getting shorter and evenings are getting cooler in temperate regions in the Northern hemisphere. This also means that the flu season will be around the corner soon. Most people group influenza (flu) and cold together and refer to the “cold and flu season” as the time of the year when we expect to come down with a “flu bug” and consider it “normal” or customary. Some are even convinced that they “never get the flu.” These attitudes presume the flu to be just like a “bad cold.” This is far from the truth: Influenza is nothing like a cold! The flu and the common cold are caused by different viruses. Although some symptoms are similar, flu has worse symptoms than the cold. Influenza infects between 5 percent to 10 percent of adults and 20 percent to 30 percent of children, causing around 3 to 5 million severe cases and about 250,000 to 500,000 deaths worldwide. In the U.S. alone,flu-associated deaths range from a low of about 3,000 to a high of about 49,000 people.
So how does the flu kill?
When people are very sick with the flu, the virus overwhelms the immune system, pushing it into overdrive that is harmful to the body. The damage occurs primarily in the lungs because they are the organ where the flu resides, but other organs can be damaged too when the immune system is in overdrive. Overwhelming inflammation in the lungs can cause severe damage to the point that it becomes impossible for oxygen to pass through the lungs and into the blood. Also, when the immune system becomes focused on killing the virus, the immune system breaks down and makes people susceptible to common bacterial infections.
Influenza worsens other medical conditions
Influenza has been widely recognized as a trigger for other diseases. It can cause a wide range of complications, including pneumonia, bacterial co-infection, cardiovascular complications and the worsening of diabetes. In a U.S. study examining the adult hospitalized cases, influenza infection with pneumonia was associated with more severe outcomes compared to cases without pneumonia. Influenza and bacterial co-infection is another important cause of morbidity and mortality among adults. Influenza-bacterial co-infections occur in approximately 15 percent of patients. Experts believe that some pneumonia cases caused by pneumococci or Staphylococcus aureus are associated with influenza infection.
Cardiovascular disease (CVD) is the number one cause of death worldwide, responsible for 17.3 million deaths in 2013. CVD is increasingly considered an inflammatory condition and is likely triggered by an acute respiratory infection: particularly influenza. It is generally believed that influenza infection induces the inflammatory release of cytokines, which results in a pro-thrombotic state and atherosclerosis, eventually leading to CVD or acute myocardial infarction (AMI or heart attack). A recent study conducted by researchers at the University of Sydney showed that the risk for a heart attack is 17 times higher during the seven days after catching influenza. This emphasizes the importance of influenza prevention, especially in people with heart problems.
People with diabetes, even when well-managed, are at high risk of serious influenza complications, often resulting in hospitalization and sometimes even death. Influenza may jeopardize the health of patients with diabetes in several ways. First, influenza may imbalance a carefully established situation of metabolic control and in some cases trigger a process of metabolic deterioration that may lead to ketoacidosis (build-up of acids in the blood) or even death. Second, diabetes might cause impaired immune responses to influenza viruses. Third, diabetes has been linked to a three times higher risk of Staphylococcus blood infection, which may cause Staphylococcal pneumonia. Influenza has been shown to be more frequent and more severe in patients with diabetes. Diabetic patients are at increased risk of complications, hospitalizations and deaths due to influenza. Once hospitalized, diabetic patients are 31 to 92 times more likely to die than other patients.
Influenza versus other viruses in the news
Other viruses like Ebola, Zika and Yellow Fever are more worrying and more important. Or, are they? The latest Ebola outbreak in the DR Congo is reminding us of the Ebola virus epidemic in 2014 in West Africa that killed over 11,300 people despite not being a respiratory virus (spread through the airborne route). The Zika virus is considered a major global health risk, as infection during pregnancy was associated with babies born with microcephaly. The 2016 yellow fever outbreak in Angola killed hundreds of people despite having a vaccine available that is highly effective (approaching 100 percent). So what about a virus that can be spread via the airborne route, survive on hard surfaces for 24-48 hours, can increase a child’s risk of a bipolar disorder if the mother is infected while pregnant, can increase the risk of fetal death and stillbirth during pregnancy and can worsen chronic medical conditions?
A virus with these features will surely be on the news and scare everyone. However, there is no need to panic; this is “just the flu.” Some good news: Good health habits like washing your hands and covering your mouth and nose when you cough or sneeze can help. The annual flu vaccine is still the best and most important step in protecting against flu viruses.
Melvin Sanicas is an infectious disease physician.
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