INFLUENZA OVERVIEW About the influenza virus.
The flu, short for influenza, is caused by two main types of virus: Type A and Type B. Both types of flu routinely spread in people, causing flu epidemics each year, but new strains of Influenza A can emerge and cause an influenza pandemic. Current subtypes of influenza A viruses found in humans are H1N1 and H3N2. In 2009, a new H1N1 virus emerged, causing the first influenza pandemic in 40 years. This new strain of H1N1 has now replaced the old strain that previously circulated in humans. Influenza B is not divided into subtypes but is broken down into lineages and strains. Two additional types of influenza, Type C and Type D, are not known to cause outbreaks, as Type C generally causes a mild respiratory illness, and Type D primarily affects cattle and is not known to infect people. The seasonal flu vaccine includes H1N1, H3N2, and one or two influenza B viruses.1
Flu outbreaks in history.
In addition to the 2009 H1N1 pandemic, the world experienced global influenza outbreaks in 1918, 1957, and 1968. The pandemic of 1968 was caused by the H3N2 virus, which is now one of the two most common strains of flu circulating today (along with the H1N1 strain that emerged in 2009). While each of these outbreaks was deemed a pandemic by epidemiologists, the 2009 H1N1 outbreak was far less severe than those that came before it. The highest estimation of total deaths from the 2009 H1N1 pandemic was about 575,000 worldwide, while the 1968 and 1957 pandemics caused about one million deaths each. The most severe pandemic in 1918 caused 50 million deaths worldwide.2
FLU SYMPTOMS
Common symptoms. When you catch the flu, the symptoms appear suddenly. People with the flu might experience fever, chills, cough, a sore throat, a runny or stuffy nose, muscle or body aches, headaches, fatigue, and more commonly in children, vomiting and diarrhea. People with the flu won’t always experience every single one of these symptoms, and it is important to note that not everyone with the flu will have a fever.3
High-risk populations. Those at higher risk of contracting the flu include adults over the age of 65, individuals with chronic medical conditions (e.g., asthma, diabetes, heart disease), pregnant women, and young children. In addition to being at a higher risk of contracting the flu, these groups of people are more likely to develop dangerous flu-associated complications than the general population, and caution should be taken if they do get sick.3
Flu-related complications: how the flu turns deadly. Flu-related complications can range from mild sinus or ear infections to serious infections like pneumonia, organ failure, and inflammation of the heart, brain, and muscles. People with a chronic disease such as asthma or heart disease might experience an exacerbation of their condition triggered by the flu. These individuals and other high- risk groups should keep in regular contact with their doctor while recovering from the flu, even if the illness is mild.
Emergency warning signs.
The flu is a common illness, with outbreaks of infection every year, but that doesn’t mean it can’t become serious enough for hospitalization. For adults with the flu, difficulty breathing, chest and abdominal pressure or pain, sudden dizziness, confusion, persistent vomiting, severe dehydration, a persistent high fever, or an improvement of symptoms that then return with fever and worsening cough are all cause for concern. Should any of these occur, seek professional help immediately. In children, these symptoms, as well as bluish skin color, refusal to drink fluids or interact with others, irritability to the point of not wanting to be held, or fever with a rash, all call for immediate medical attention. Infants with the flu that are unable to eat, have trouble breathing, or have no tears when crying (a sign of severe dehydration) require immediate medical attention.3
PREVENTION
The flu vaccine. Fortunately, the current flu vaccine contains inactivated versions of flu strains that have caused pandemics in the past and have been deemed by experts to be the most prevalent strains. The vaccine causes antibodies to develop in the body about two weeks after vaccination. The flu vaccine changes every
year in order to reflect changes in the particular strains circulating that year, and the CDC provides frequent updates about the efficacy of the vaccine every year. During a particularly active flu season (such as the one we have seen this year) the CDC will release weekly updates regarding vaccine efficacy.
Recent studies have determined that the vaccine reduces the risk of flu illness by about 40 to 60 percent. However, even if the circulating virus is different from the administered vaccine, the vaccine can still provide some protection. While these odds might seem unimpressive, the flu shot can still offer some protection even if you still get sick. For those who fall ill even after vaccination, the vaccine can reduce the risk of flu-associated hospitalization, and this benefit holds true among vulnerable populations such as children, older adults, and those with chronic health conditions, such as heart disease, diabetes, and lung disease. Pregnant women who receive the vaccine are protected before and after pregnancy, and the expecting mother will pass these antibodies onto the developing baby, keeping the infant protected even after birth. It is important to note that children younger than six months are too young to receive the vaccine but are still at high risk for serious flu illness. Pregnant women are not only protecting themselves from the flu but are also fortifying their infant children against the illness.4
A recent study published in 2017 in the medical journal Pediatrics concluded that the flu vaccine reduces the risk of flu-associated death in healthy children by 65 percent. During this four-year study period, 358 confirmed flu-associated pediatric deaths were reported, and only 25 percent of those patients had received the flu vaccine.5
In addition to ever-changing flu strains, the body’s immune response from the vaccination declines over time, so just because you were vaccinated last year does not mean you’re fully protected for the coming year. Taking into the consideration the two-week period that the body requires after vaccination to build up antibodies, it is recommended that people get the flu vaccine by the end of October. However, experts recommend that even those who haven’t received the vaccine within this time frame should get vaccinated at any time during flu season. Keep in mind that even after receiving a flu shot, you will not be protected immediately.4
A common myth associated with the flu shot is the possibility of actually catching the flu from the vaccine. This, thankfully, is not true, according to the CDC. Flu vaccines contain inactivated viruses that are not infectious; some vaccines, known as recombinant influenza vaccine, do not contain viruses at all. Most people who claim to have gotten the flu from the flu shot are experiencing the side effects that are known to accompany the shot, including a low-grade fever and aches. These symptoms are mild and subside in a few days.4 Not sure where to get vaccinated for the flu? The CDC’s website provides a list of nearby locations based on your zip code where flu shots can be obtained. Visit cdc.gov/ flu for more for more information.
Get your vitamins. In addition to the flu vaccine, the Cleveland Clinic recommends taking multivitamins, eating a diet rich in colorful foods (i.e., a diverse mixture of fruits and vegetables), and paying special attention to the amount of vitamin D that you are consuming, ensuring that you receive 1,000 IU per day.7,8
Vitamins A, C, and E also play a crucial role in supporting the immune system and can fortify
your body against the flu virus. While vitamin and multivitamin supplements are useful in ensuring you’re getting these flu-fighting nutrients, eating foods naturally rich in these compounds is the healthier choice, and supplementation can be used to close any nutritional gaps. Check out the separate article in this issue dedicated to nutrition and the immune system to learn more.
Exercise is a flu shot’s best friend. With a 40- to 60- percent success rate, a flu shot isn’t a surefire way to avoid catching the flu, but studies have shown that exercise can strengthen the effectiveness of the flu vaccine. One study from 2009 showed an increased antibody response in 144 sedentary, healthy older adults who participated in 10 months of regular, moderate cardiovascular exercise after receiving a flu vaccine. If they did get sick, participants in this study reported reduced overall illness severity and reduced sleep disturbance; this suggests that if participants did fall ill, they were able to rest and recover more effectively.9,10
An even more notable study that took place at Iowa State University required participants to either complete a 90-minute block of exercise 15 minutes following their flu shot or sit quietly for 90 minutes following their shot. Researchers measured the levels of influenza antibodies in these two groups a month later, and these tests showed influenza antibody levels were almost doubled in the group that exercised directly after getting the shot. Follow- up studies sparked by this initial study concluded that 90 minutes is definitely the optimal amount of exercise in order to create this robust antibody response; a three-hour block of exercise actually weakened the immune response, while 45 minutes showed an improved, but less notable antibody response. Researchers who led this study believe this strategically planned exercise session, which sped up blood circulation, moved the vaccine from the injection site to the rest of the body more quickly and thoroughly. In light of this impressive evidence, consider taking a brisk 90-minute walk or bike ride after your next flu shot to boost the vaccine’s benefits for the rest of the season!9,10
RECOVERING FROM THE FLU
Despite our best efforts to prevent catching the flu, some of us will still get sick. In cases of illness from flu, you should first assess your symptoms to determine the best course of action. Many people who catch the flu will experience a mild form of the illness, with symptoms requiring bed rest at home. For individuals in high- risk groups, it’s best to visit the doctor right away. In addition, if symptoms are particularly concerning or more severe than the usual aches and pains, err on the side of caution and take a trip to your doctor’s office. If you do decide to see your doctor, he or she might prescribe an antiviral medication, which can, in some cases, speed recovery and help prevent flu-associated complications. It is recommended that those infected with the flu stay home for at least 24 hours after their fever has broken on its own without use of any fever-reducing medicine. During this time, minimizing contact with others is important to help avoid spreading the virus.
Exercise: take a break. Here at Nutrition Health Review, we are big advocates for exercise. However, when suffering from the flu, even the most dedicated fitness fanatics need to rest. According to experts interviewed by the Los Angeles Times, the concept of “sweating out” the flu with exercise is a myth. During exercise, body temperature goes up. Pairing this with an existing fever might lead to overheating and intense dehydration, which can weaken the immune response. If you really feel the need to exercise while fighting the flu, doctors suggest doing no more than some light stretching. Avoid going to the gym until you’re fully recovered—your fellow gym members will thank you.11
Feed that fever! The antedote “Feed a cold, starve a fever!” (or is it “Starve a cold, feed a fever!”?) is only half right. When your body fights any illness, it needs energy, and eating a well-balanced diet will help your body win the battle. When you have the flu and are experiencing a fever, the increased body temperature actually speeds up the metabolism, resulting in an increase in the number of calories you’re burning while lying in bed. This makes restoring those burned calories vital to recovery. Be sure you’re taking in a balanced diet of protein, carbohydrates, and healthy fats to keep your body nourished. In addition to maintaining a healthy diet while fighting a fever, be sure to drink plenty of fluids, preferably water or green tea, which will provide the added benefits of antioxidants. You might not feel like eating or drinking much while sick, especially if you have a fever, but keeping your body properly fueled and hydrated will encourage a speedier recovery and quicker end to your suffering.12
SUMMARY
Protect yourself against the flu by maintaining a regular moderate exercise regimen, eating a well- balanced diet rich in whole foods and fresh fruits and vegetables, staying hydrated, and getting adequate rest. And just as importantly, get your flu shot! While complete immunity isn’t guaranteed with the flu shot, it significantly decreases your vulnerability to the virus. Exercising for 90 minutes after getting the flu shot will boost your body’s antibody response to the vaccine, so plan to get vaccinated on a day when you’ll have time for a workout. Get in the habit of washing your hands regularly and sanitizing communal surfaces. And finally, if you do catch the flu, stay hydrated, maintain a healthy diet, and take a break from exercise until recovered, especially if feverish.
