This Is What Happens When a Virus Invades Your Immune System

In the wake of COVID-19, immune health isn’t a seasonal concern. It’s a global obsession.

That’s why we’re rolling out our most comprehensive coverage ever on immune health. We’re here to offer you a refresher and add some new intel to your arsenal of knowledge. Because knowledge is vital for good health—and a stronger-than-ever immune system.

If your body’s cells were a car or plane, you’d be right to refer to viruses as hijackers. After all, viruses only survive if they can find a likely carrier (living, normal cells) to take over. If the carrier allows entry, the virus can then kill, damage, or change the cells in its quest to survive and multiply—making you sick in the process. But if the carrier (you) has a good defense system (your immune system), then the hijacker is more likely to be defeated.

“Your immune system is your interface with the environment,” notes Andrew Weil, MD. “If it’s healthy and doing its job right, your body can interact with germs and not get infections, with allergens and not have allergic reactions, and with carcinogens and not get cancer. A healthy immune system is the cornerstone of good general health.”

Two main types of germs routinely challenge the immune system: bacteria and—most famously of late—viruses.

Even if you have a strong immune system, sometimes the virus is a successful hijacker. But the immune system doesn’t just give in; it goes into overdrive to get rid of the thief. Our normal white blood cell (leukocyte) count is about 5,000 to 10,000 per cubic millimeter of blood. When we get sick, this number skyrockets as our immune system produces more white blood cells to respond to the virus.

These cells immediately set out to defeat the hijacker … and that’s when we get all those annoying symptoms. “Symptoms like a stuffy nose or fever are actually the result of your immune system going to work,” says Dr. Thomas S. Ahrens, a fellow of the American Academy of Nursing and international researcher.

Often very easily. For example, with one sneeze, we can eject up to 20,000 droplets that could contain hijacking viruses like rhinovirus or COVID-19. Someone needs only to touch or breathe in these particles to give the virus the opportunity to hijack its next victim.

Look for part two of our special series on immune health in mid-April. You’ll learn more about lifestyle habits to protect yourself.

13 immune system stars

1. Chaga mushroom

A potent immune strengthener, chaga can help us ward off harmful pathogens thanks to its antiviral activity—without toxic side effects. It can also help reduce inflammation in the body.

2. Echinacea

Extracts of the herb echinacea have demonstrated a positive effect on the immune system by increasing the number of white blood cells, which fight infections. In a 2014 review of 24 studies involving more than 4,500 subjects, echinacea was found to help in preventing colds.

3. Folate

Otherwise known as vitamin B9, folate is essential to DNA synthesis and cell growth. Deficiency is thought to hamper immunity.

4. Lysine

One of the essential amino acids (protein building blocks), lysine plays an important role in the immune system. Food-wise, lysine is available primarily in meat and dairy products, so those on a plant-based diet may want to take it in supplement form (L-lysine). The best vegan food sources of lysine are legumes.

5. Oil of oregano

Oil of oregano has long been used for the symptoms of colds, flu, bronchitis, and other respiratory complaints because of its anti-inflammatory, antiviral, and antibacterial properties. According to researchers, carvacrol—an important constituent of oregano oil—has a unique way of breaking down the external proteins of the norovirus (a notoriously contagious virus that causes vomiting and diarrhea), allowing the internal part of the virus to be killed.

6. Probiotics

These beneficial bacteria may be found in foods like vegan yogurt with live cultures, as well as in fermented vegetables like sauerkraut and pickles. Probiotics are also sold as capsules, tablets, liquid supplements, and loose powder. Probiotics can help promote immune health by secreting protective substances in our gut that then activate the immune system, preventing pathogens from taking hold.

7. Quercetin

Quercetin is a powerful antioxidant found in citrus fruits, and preliminary research shows it may stop the rhinovirus in its tracks by preventing it from replicating and spreading. (The rhinovirus is the most common cause of upper respiratory infection, aka the common cold.)

8. Selenium

Selenium is an important trace mineral for human functioning, including immunity. Selenium is found in foods like nuts, seeds, and brown rice and in supplement form. Selenium has been the subject of ongoing studies focusing on its beneficial impact on white blood cells and immunity.

9. Vitamin B complex

The B-complex family includes eight vitamins, all of which work together to convert the food we eat into fuel. A lack of B vitamins like B12 and B6 has been linked specifically with poor mood and a decrease in immunity. Because B12 is found mainly in animal products, vegans need an extra boost (aka supplements), as may older people who are more at risk of B12 deficiency.

10. Vitamin C

An antioxidant that can be taken as a supplement on an ongoing basis to stimulate components of the immune system, vitamin C may help shorten the duration of the common cold. Bonus: Research has shown that people with higher vitamin C stores have lower risks of hypertension, coronary heart disease, and stroke.

11. Vitamin D

Supplementing with vitamin D helps ensure we get enough in our system, since sun exposure can be a challenge for many and food sources are few. Studies have shown that vitamin D can strengthen our immunity to infections due to vitamin D receptors on cells of the immune system.

12. Vitamin E

This super antioxidant is also involved in boosting the body’s immune function, helping to fight off bacteria and viruses. Vitamin E is also important for healthy skin and eyes. Good food sources of vitamin E include vegetable oils, green leafy vegetables, red bell peppers, seeds, and nuts.

13. Zinc

Research has demonstrated that people who supplement with zinc seem to catch fewer colds, and those who already have colds experience reduced duration and symptoms with zinc supplementation. Zinc stimulates the production of our own immune cells so we have a better defense against viruses and bacteria.