04/25/2016 11:23 EDT | Updated 04/26/2017 05:12 EDT

This Is What Happens To Your Lungs When You Get The Flu

Sebastian Kaulitzki via Getty Images
lung infection

We haven't heard much about influenza this winter. According to the latest statistics, it has been a relatively quiet year with 4,371 hospitalizations and only 193 deaths.

While these numbers are concerning, they pale compared to last season in which some 8,000 people went to hospital and 600 died.

The impact of the flu on the population does change from year to year; it's normal. A combination of factors such as climate, travel and the nature of the virus itself all contribute to determining whether a specific season will be mild or severe. But while the population-based perspective does happen to fluctuate over the years, for those who are infected with the virus, the symptoms are, for the most part, the same.

The most common complaint is congestion in the chest and the lungs. For some, the feeling is akin to having a person sitting on the chest, making it hard to breathe. Fatigue and despair comes next, which can keep a person feeling lethargic for days. Eventually, the body seems to be trying to shut down as the virus continues its campaign.

This process can last for days to weeks and may become so bad hospitalization is needed. If the symptoms do not resolve quickly enough, the situation may become life-threatening.

A detailed account of what happens at the site of battle has been for the most part a mystery.

While these outward symptoms have been known for decades, little has been known in terms of what is actually causing these troubles at the cellular level. Researchers have known the immune system plays a role in fighting the virus and other parts of the body do change. But a detailed account of what happens at the site of battle has been for the most part a mystery.

Now an international team of researchers have given us a glimpse into the war happening inside. Last week, they published the results of a new type of microscopic investigation of the impact of flu on the body. Their findings offer insight into the process and more importantly, why we experience severe symptoms and how we ultimately may be able to prevent them.

The group used a relatively new technique to examine and identify up to a thousand proteins at the same time. The technique has been used to identify particular proteins involved in a variety of chronic ailments including tuberculosis, cancer and Alzheimer's disease. For the researchers, this platform offered the perfect opportunity to identify these "biomarkers" and learn about how the lungs react to influenza virus infection.

The experimental design was straightforward. Respiratory samples were taken from patients with confirmed influenza virus infection and brought to the lab. Here, the samples were diluted in half and then analyzed. A total of 18 samples were used to ensure results were common amongst various individuals. Another six samples from healthy individuals were also analyzed as a control. After the testing was complete, the team then matched any identified proteins with their function in the hopes of developing a better picture as to what happens in the lungs.

The team identified 160 human proteins involved in influenza infection. Individually, these proteins offered an interesting picture about the response to viral infection. But when the team matched biomarkers to mechanisms, the end result revealed how influenza doesn't simply cause a battle: it sparks a war.

Many of the proteins found are involved in stress response. But stress at the cellular level can be troublesome. The proteins were involved in a variety of critical pathways such as airway inflammation. In this case, influenza infection led to an increase in a protein known as MSK1. This in turn can cause symptoms similar to those of asthma.

Another protein biomarker, kininogen, is involved in blood coagulation and vessel dilation. The flu triggers the body to open up arteries and veins allowing more blood to flow but also instigate the onset of fever. This factor may also help to trigger the release of fluid into the respiratory system.

The majority of proteins found in the analysis were members of the immune system. This was no surprise. But the function of these proteins was somewhat unexpected. Instead of participating in combat, these proteins were sending out mayday signals to a particular type of immune cell known as a co-ordinator of antiviral activity.

It's called a memory T-cell. It is responsible for identifying already known enemies and then conducting a proper engagement to ensure victory. Memory T-cells are perhaps the most important in the battle against influenza as they can help determine whether the outcome will be routine or, if there is no memory, severe. In essence, having memory is the best way to fight influenza.

The results of the study offer a look at the localized battlefield during flu infection. However, the results have an even greater relevance by giving us an idea of what to expect when we get the flu.

Most importantly, this study highlights how the body depends mostly on memory to help battle the virus. Thankfully, we already know a way to get those memory cells long before we come into contact with the virus: vaccination. Based on the results of this study, vaccination may be the best way to stay safe during flu season.

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