What Is Adenovirus? Symptoms, Vaccines, and Treatment

While adenovirus have been around for eons, it’s likely you’ve only heard the name recently. That’s because the Centers for Disease Control and Prevention and other organizations are investigating a recent spike in cases of hepatitis of an unknown origin that have appeared in children. Because some of these individuals tested positive for adenovirus, there could be a connection between the virus and the liver disease.

But what exactly is adenovirus?

“Adenovirus is actually a short name for a DNA virus,” says Dr. Daniel Ganjian, a pediatrician at Providence St. John’s Health Center in Santa Monica, California. A DNA virus’s genome is made of deoxyribonucleic acid. Other examples of DNA viruses include herpes viruses, small pox and papilloma viruses. This is in contrast to some other types of viruses such as COVID-19, measles and rabies, that are RNA viruses. These contain ribonucleic acid as their genetic material.

Adenoviruses can cause a variety of ailments, especially because there are so many of them. “There are at least 50 types of adenovirus that we know of,” says Dr. Wassim Ballan, a pediatric infectious diseases specialist at Phoenix Children’s Hospital in Arizona.

In fact, “adenovirus infections are some of the most frequent infections in humans,” says Dr. Luis Ostrosky, an infectious disease specialist with UT Health Houston, Memorial Hermann Hospital in Houston. “The adenovirus family contains multiple viruses that can cause disease in humans ranging from respiratory illness, diarrhea and skin infections to more severe infections like meningitis and hepatitis.”

[SEE: 9 Myths and Misconceptions About the Flu Vaccine.]

Adenovirus Symptoms

Adenoviruses circulate in the environment regularly, and you likely come into contact with them fairly regularly. If you haven’t encountered that strain before and don’t have immunity built up to it, it could make you sick.

“The symptoms depend on which strain you’re infected with,” says Dr. Karen Acker, a pediatric infectious disease expert with Weill Cornell Medicine and New York-Presbyterian Hospital Weill Cornell Medicine in New York City. “Some strains cause common cold symptoms and respiratory symptoms, others cause conjunctivitis (pink eye) and some strains cause vomiting and diarrhea.”

Dr. Esther Kim Liu, chair of the department of pediatrics at the UM Baltimore Washington Medical Center in Glen Burnie, Maryland, says that most of the time, infection with adenovirus is mild. But “young infants or those who are immunocompromised are at risk for severe illness.” This can lead to other conditions, including:

Pneumonia. Pneumonia occurs when the air sacs inside the lungs become inflamed. They also may fill with fluid or puss, making breathing difficult and causing coughing, fever and other symptoms. Pneumonia caused by adenovirus “can occasionally be severe, requiring hospitalization and can occur in outbreaks,” says Dr. Andrew Pavia, chief of the division of pediatric infectious diseases for University of Utah Health and director of the hospital epidemiology program at Intermountain Primary Children’s Hospital in Salt Lake City.

Intussusception. This potentially life-threatening illness causes one part of the intestines to slide into another part of the intestine, causing an obstruction that prevents food from passing through the intestinal tract.

Encephalitis or meningitis. Encephalitis is an inflammation of the brain and meningitis is a swelling of the meninges, which is the membrane that surrounds the brain and spinal cord. Both can be very serious illnesses.

[SEE: Best Foods to Eat for an Upset Stomach.]

How Is Adenovirus Transmitted?

Acker notes that some strains are transmitted via respiratory droplets from the mouth or nose. “When you cough or sneeze, these droplets can infect someone else if they get into another person’s mouth or nose.”

In contrast, “gastrointestinal strains are spread by the fecal-oral route and transmission occurs if someone does not wash their hands well after using the bathroom and then touches someone else or prepares food for another person.”

Dr. Brandi Manning, an infectious diseases physician at the Ohio State University Wexner Medical Center in Columbus, adds that “the type that causes conjunctivitis is contagious with close contact and then touching one’s eyes or getting infected fluid in the eye.”

Because adenovirus can be so easily transmitted “handwashing is key to preventing transmission and infection,” says Ballan says.

[SEE: 7 Foods That Are Good for Your Liver.]

How Is Adenovirus Treated?

Currently there are no approved adenovirus treatments for adenovirus infections for the general public. In some cases, antiviral medications may be offered to immunocompromised patients with very severe disease, but most of the time, the virus runs its course and you get better.

For most people, if your symptoms are bothersome but not too severe, Ballan recommends “over-the-counter medications for fever (such as acetaminophen), staying well-hydrated, monitoring breathing and proper and frequent handwashing to prevent transmission.

“The main treatment is supportive care,” Liu says. “This means ensuring that children are well hydrated and that their symptoms such as sore throat, cough or diarrhea are managed.”

The same goes for anyone who feels ill because of an adenovirus infection. “For most people with an adenovirus common-cold-like illness, lots of rest and fluids is usually key. If anyone develops shortness of breath or other severe symptoms, then an evaluation by a clinician would likely be appropriate,” Manning says.

Who Is Susceptible to Adenovirus?

Liu says that adenovirus “can cause infections in people of all ages,” but it’s “most commonly seen in babies and young children.” That’s in part because adenoviruses are highly contagious and in schools, day care settings and at summer camps, it’s very easy for the virus to jump from one child to another.

Close quarters can also contribute to outbreaks of adenovirus in adults, Pavia says. “Outbreaks of certain types of adenovirus have caused severe pneumonia in military recruits, where crowding and the physical stress of basic training are felt to contribute.”

People with weakened immune systems are also at higher risk of getting sick from adenovirus. People undergoing treatment for cancer, those who’ve had organ transplants and individuals with inflammatory conditions or genetic immunodeficiencies are at higher risk of developing severe or life-threatening diseases from adenovirus infection.

The Connection With Hepatitis

Ganjian explains that in October 2021, doctors around the world began observing “a slightly increased number of kids with hepatitis,” which is inflammation of the liver. It can be caused by many things, but this slight increase was concentrated in otherwise healthy kids, and the illness wasn’t easily explained by another conditions.

“Some of these children did have positive tests for adenovirus and so there is a possible link, but we need more information before we can make any conclusions,” Manning says.

Therefore, the CDC is currently investigating whether those hepatitis cases among kids stemmed from adenovirus infections, with a specific strain called adenovirus 41 being the possible culprit.

Dr. William Balistreri is director of the division of pediatric gastroenterology, hepatology and nutrition at Cincinnati Children’s Hospital Medical Center in Ohio. Balistreri notes that while adenovirus 41 could be behind this spate of cases, it could be a new variant or it could be a combination of another various that is co-infecting these kids and leading to the liver problems.

“We know that viruses can have long-term effects,” he says. For example, some people end up with “long-COVID,” and other viruses, such as polio, have well documented long-term health implications that can arise months or even years after the acute infection has resolved.

It could be that kids who had COVID-19 and later get infected with a certain adenovirus are at higher risk of developing hepatitis. It could be another virus at work. Or it could also be simply that people are becoming more aware of the potential complications of adenovirus, Balistreri says.

For example, one patient he saw in March was referred to him by a primary care provider when the child came into the office for flu-like symptoms. The provider ran some tests and discovered that the boy’s liver enzymes (a measure of possible liver damage and that could be a sign of hepatitis) were “sky high.”

Balistreri asked the other doctor whether he would have tested the liver enzymes if he hadn’t been aware of a possible connection between adenovirus and hepatitis, and the other doctor said he would not have. “So, I suspect there have been cases in the past that were dismissed as having a flu-like illness and no one measured their liver enzymes,” he explains.

In fact, it would have been easy to miss in this particular patient, he says. “When I saw that boy, he looked great. I probably wouldn’t have measured his liver enzymes either,” as he didn’t have any obvious signs of liver disease, such as yellowing of the eyes or skin, Balistreri says.

Still, it’s “very rare to see adenovirus cause such a strong complication in people. Usually, it’s very mild and almost all recover from it,” Ganjian says and it’s worth keeping an eye on. This is why the CDC is investigating.

While there has been an increase, Ganjian emphasizes that there’s no reason for parents to panic. “I don’t want people worrying about this. You already have the best way to prevent infection, which is good hygiene and taking care of yourself.”

Balistreri agrees there’s no need to freak out. “I don’t want to alarm parents and I don’t want them to panic and inundate practitioners’ offices.” Instead, keep in regular contact with your child’s pediatrician and if your child develops symptoms that are worrisome or severe, reach out for guidance.

Especially, “if the patient develops jaundice, which is yellow eyes, yellow skin and dark urine, that should be investigated. There is a small percentage of these children that may progress” into liver damage, and being able to intervene as early as possible offers better outcomes.

Most children who develop hepatitis won’t need a transplant; the liver can heal over time and “most of these patients, even those that develop injury will do fine. They will recover. But that needs monitoring and hydration and the close attention,” he says.

The Connection to COVID-19 Vaccines

If you’re wondering, “wasn’t adenovirus used in one of the COVID-19 vaccines?,” you’re absolutely correct. The Johnson & Johnson COVID-19 vaccine is a viral vector vaccine, also called an adenovirus vector vaccine, that uses adenovirus as the delivery vehicle for the vaccine in the body.

But don’t worry: That adenovirus vector vaccine won’t make you sick and there’s no evidence that it can contribute to the development of hepatitis or any other disease. “These artificially constructed adenoviruses do not replicate in the host or cause infection. They degrade after they accomplished their function,” Ostrosky says.

Liu explains that virus-vector vaccines like the J&J COVID-19 vaccine are like Trojan horses in that they “sneak the code into your cells so you can protect yourself without actually being infected.”

Essentially, using bioengineering tools, scientists “took the structure of the adenovirus and emptied out the inside of it — the stuff that causes the virus to make people sick — and replaced it with vaccine information,” Ganjian says. This approach is used in several other vaccines, such as a vaccine for tuberculosis.

In the case of the COVID-19 vaccine from J&J, the information put inside the hollowed out adenovirus is the RNA code for the spike protein on the outside of the coronavirus, SARS-CoV-2, that causes COVID-19. That information instructs the body to generate the antibodies needed to prevent the spike proteins on the coronavirus from lodging in your cells if you’re exposed to it.

This adenovirus vector vaccine uses a different approach from the Moderna and Pfizer COVID-19 vaccines, which are mRNA vaccines. That’s a different technology that contains no elements of adenoviruses.

In all cases, this vaccine-based version of an adenovirus won’t make you ill. “When used as a delivery system, the adenoviruses are modified in a number of ways so that they cannot make the recipient sick,” Pavia says,

Prevention Is in Your Hands

Adenoviruses are super common and can cause a wide range of illnesses, but you can prevent infection by taking care of yourself and engaging in good handwashing and hygiene practice, Ganjian says.

He adds that an adenovirus vaccine does exist, but it’s not available to the general public. Instead, it’s reserved for members of the military to reduced illness when in close quarters for training and service.

For those not in the military, “the most important thing to remember is if you experience symptoms of adenovirus infection, please practice proper and frequent handwashing to prevent transmission,” Ballan says. And if your symptoms are severe, seek medical attention.

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What Is Adenovirus? Symptoms, Vaccines, and Treatment originally appeared on usnews.com

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