Most people think that viruses — such as Ebola, hantavirus, SARS, West Nile, and influenza — kill people directly. In their minds, it is the virus itself that actually kills a person.

But, in fact, recent studies have shown that most viruses kill by causing the body to overreact to the infection.

In essence, it is your immune system that makes you sick, and eventually can kill you. Studies have shown that in many cases the virulence of a virus is actually based on its ability to trigger immune overreaction.

In a high percentage of cases, a person’s immune system is not operating normally.

Part of the immune system, usually the cellular immune system, is weakened either by heredity, other illnesses, poor nutrition, or aging. And the intact parts of the immune system overreact to correct the defect.

In the process, the dysfunctional immune system produces enormous waves of pro-inflammatory immune chemical signals called cytokines and chemokines.

The pro-inflammatory cytokines cause intense inflammation, and the chemokines attract more immune cells to the site, thus worsening the inflammation. We call this abnormal reaction to infections a “cytokine storm”.

The lungs of a person who is extremely ill or who has died of influenza are filled with thick proteinaceous fluids packed with numerous white blood cells and areas of hemorrhage.

These masses of inflammatory products block the alveoli and shut off the oxygen supply, causing suffocation.

If this immune overreaction is not contained, the cytokine storm can spread throughout the body, destroying multiple tissues and organs — a process called multiorgan failure.

This is the main cause of death in many viral infections such as Ebola, other hemorrhagic fevers, and severe cases of influenza.

In studies of nonhuman primates infected with the 1918 pandemic influenza virus, researchers found very high levels of TNF-alpha and interleukin-1-beta — both powerful inflammatory immune cytokines — throughout the animals’ bodies.

The same elevation of inflammatory cytokines is seen in SARS, West Nile, hantavirus, virulent influenza, and Dengue fever.

Reducing these cytokines dramatically improves a patient’s chances of survival, even when the virus is not cleared from the system.

In fact, the amount of virus (called the viral load) doesn’t always matter. Even low viral loads can trigger intense cytokine storms.

Interestingly, the Ebola virus can only invade one of the many types of white blood cells — the macrophage.

Early in the infection, there is a tremendous disappearance of T-lymphocytes, which are one of the most effective white blood cells in killing Ebola or any other virus.

During recovery, the T-lymphocytes increase in the blood and tissues. By infecting the macrophage and reducing the number of T-lymphocytes, the virus is suppressing the person’s immune system, allowing the virus to multiply enormously.

But because not all parts of the immune system are suppressed, the remaining healthy immune cells secrete enormous amounts of pro-inflammatory cytokines and chemokines. This is what destroys organs and tissues in people dying of an infection.