Why Is Rabies so Deadly, What Are the Symptoms in Humans As Man Dies in Illinois

A man in Illinois has become the first person to die from rabies in the state since 1954, according to the state's health department.

The victim—a man in his 80s from Lake County—began experiencing symptoms consistent with the disease around a month after waking up to find a bat on his neck. He subsequently died, according to the Illinois Department of Public Health (IDPH).

The bat in question was captured and tested positive for rabies. Health officials told the man that he needed to start post-exposure rabies treatment, but he declined.

Rabies is a serious viral disease that affects the brain and spinal cord of mammals. The virus is usually transmitted when people are bitten by an infected animal. In the U.S., where dogs are routinely vaccinated against rabies, this animal tends to be a bat.

Once symptoms appear, the disease is almost always fatal in humans. The disease is preventable, however. People who are exposed to the virus must receive treatment as soon as possible to prevent the development of disease.

Why is rabies so deadly?

When the rabies virus enters the body through the saliva of an infected animal, it travels from the site of exposure to the brain via the nerves and the spinal cord. Before the virus reaches the brain, the infected individual does not usually experience any symptoms.

Typically, the virus takes three to 12 weeks to reach the brain depending on the site of exposure and other factors, although this period can be as short as a week and as long as a year or more in rare cases.

When the virus reaches the brain, it multiplies there rapidly causing inflammation before passing to the salivary glands and the saliva. Once the virus starts affecting the brain people begin to develop symptoms and from this point, the disease is almost always fatal.

The reason the virus is so deadly is that causes significant and progressive damage to the brain and spinal cord, as well as the fact that people show no symptoms until the pathogen has reached the brain—at which point, it is almost always too late to prevent death.

"The thing about the rabies virus is that it has a preference for nervous tissue," Jimmy Whitworth, a professor of international public health at the London School of Hygiene & Tropical Medicine, told Newsweek.

"It gets into nerves around the bite site and makes its way over a few days or weeks into the brain and spinal cord. Once this happens then it is virtually always fatal."

What are the symptoms of rabies?

The brain damage caused by rabies produces a variety of symptoms. The initial signs of the disease are fever with pain and an unusual tingling, prickling or burning sensation at the site of exposure.

As the disease develops, patients experience one of two distinct forms of the disease: furious rabies and paralytic rabies.

The signs of furious rabies include hyperactivity, excitable behavior, hydrophobia (fear of water) and sometimes aerophobia (fear of drafts or fresh air). In these cases, death usually occurs within a few days of symptoms developing due to cardio-respiratory arrest.

In paralytic rabies—which accounts for around a fifth of cases in humans according to the World Health Organization—the disease takes a longer course. The muscles of the patient gradually become paralyzed starting at the site of exposure. They eventually fall into a coma and die.

"Rabies has the highest mortality rate of any disease," Dr. Ngozi Ezike from the IDPH said in a statement.

"However, there is life-saving treatment for individuals who quickly seek care after being exposed to an animal with rabies. If you think you may have been exposed to rabies, immediately seek medical attention and follow the recommendations of health care providers and public health officials."

Human rabies cases are very rare in the U.S., with only one to three cases reported annually, according to the CDC.

Whitworth said: "Vaccination, as soon as possible after the bite exposure is highly effective at preventing disease. Washing the bite site thoroughly with soap and water as soon as possible is also highly recommended to prevent the virus from getting into the body."

A bat
Stock image showing a bat. These animals can transmit rabies to humans. iStock