Norovirus

What is Norovirus?

Noroviruses are a type of virus that do not have a protective outer layer, and carry their genetic material in single-stranded RNA. This virus family, named Caliciviridae, was first identified in 1968 after an outbreak of stomach and intestinal inflammation, also known as gastroenteritis, in Norwalk, Ohio. Hence, the virus was named the “Norwalk virus”.

Norovirus is a usual cause of sudden stomach and intestinal illnesses globally. In developed countries where there are vaccination programs against the rotavirus, another virus that causes gastroenteritis, norovirus has become the most common cause of this illness in children.

The common signs of infection from the norovirus include feelings of nausea, episodes of vomiting, and diarrhea. These symptoms could lead to severe dehydration that might require hospitalization.

Beyond the physical effects, norovirus also has a significant financial impact in developed countries.

What Causes Norovirus?

Norovirus, a common cause of stomach upsets, comes in seven different types, but two – genogroup I and II, are responsible for most human cases. There are just a few cases caused by norovirus GIV. Of all these types, a specific strain under genogroup II, known as norovirus GII.4, is the one that often leads to most human outbreaks. Additionally, this particular strain, GII.4, tends to cause more serious symptoms and has a higher risk of leading to death compared to other strains.

Research has pointed out that outbreaks of norovirus caused by contaminated water are likely to be from genogroup I strains, while healthcare-related and winter outbreaks are more commonly caused by genogroup II strains. These different types of noroviruses are classified based on differences in two of their proteins, VP1 and ORF1.

Norovirus primarily spreads through the fecal-oral route, which means it can spread by consuming contaminated water or food, or direct contact with a contaminated surface or an infected person. The virus is tough and can survive on surfaces even after they’ve been disinfected. The virus also does not need many particles to cause an infection – as few as ten viral particles are enough to cause infection.

Risk Factors and Frequency for Norovirus

Norovirus causes an estimated 21 million cases of stomach and intestine-related illnesses in the U.S. every year. It’s thought to be the cause of around 60% of acute gastroenteritis cases in the U.S., leading to 400,000 emergency room visits and 71,000 hospitalizations each year. Outbreaks often start from food that has been contaminated during its production or preparation, particularly with foods consumed raw, like fruits, vegetables, oysters, and fish.

• Outbreaks of the illness often occur in a variety of settings, including hospitals, schools, military barracks, cruise ships, and resorts.
• The most common way it spreads is from person-to-person, but it can also come from touching infected surfaces.
• Good hand hygiene and keeping surfaces clean is very important during an outbreak.
• Health experts recommend washing hands with soap and running water for at least 20 seconds.
• Alcohol-based hand sanitizers can help, but they should be used in addition to washing hands with soap and water.
• Places like sinks, toilets, tables, chairs, and beds should be cleaned with a bleach solution.
• If items have been noticeably contaminated with vomit or stool and they can’t be properly disinfected, they should be thrown away.

Everyone’s at risk for catching norovirus, but people on either end of the age spectrum and those whose immune system isn’t strong are the most likely to have serious health problems because of it. For example, older adults and newborns are more likely to have complications. Additionally, the disease is more common in developing nations. It’s critical to note that people with weakened immune systems from conditions like HIV/AIDS and cancer, have a higher chance of getting infected by norovirus, are more likely to have complications, and may carry the virus for longer without any symptoms.

Signs and Symptoms of Norovirus

It’s crucial to examine the patient’s medical history and conduct a physical exam when trying to figure out the cause of abdominal pain or gastrointestinal issues. An infection with norovirus often leads to a condition called gastroenteritis. If you have this illness, you could experience a variety of symptoms:

• Nausea
• Vomiting
• Stomach pain and cramping
• Diarrhea
• Body aches
• Headaches
• Chills

Some people might have more diarrhea while others could feel bouts of vomiting. These symptoms can start suddenly and usually last between 1 to 3 days. When a doctor examines you, they might not find any specific points of tenderness, but if your abdomen feels significantly tender or shows signs of inflammation, they would have to look for other potential diseases. Similarly, if you have bloody stools, it is also an indication that more tests are needed.

Depending on how well hydrated you are, you could also show signs of dehydration like a fast heart rate, lower than normal blood pressure when you stand up, wrinkled skin, and dryness inside your mouth. In rare cases, some people might also get severe neurological symptoms like seizures or brain disorders.

When you consult with your doctor, they might ask you about where you live (for example, a nursing home or military barracks), your water source (river, city water, or well), your recent travels, if you have taken antibiotics recently, ate uncooked or raw food, or had exposure to anyone who was also sick. It will also be important for them to know if your immune system is compromised as it could mean your illness could last longer and have more serious consequences.

Testing for Norovirus

Many people with norovirus, a common stomach bug, don’t actually go to the doctor for a diagnosis. This is because the symptoms are usually mild and go away on their own. However, if you do see a doctor, they will likely approach it as they would a case of gastroenteritis, which is inflammation of the stomach and intestines, often caused by an infection.

Usually, there’s no need for any diagnostic tests. However, in some cases, a doctor might ask for a metabolic panel. This is a blood test to check for hydration and electrolyte balance, which might be off due to symptoms like vomiting and diarrhea.

It’s unusual for a doctor to order other stool tests unless your symptoms last for a long time or they suspect a different illness. If they think you have norovirus, they have a few options for tests. These include enzyme immunoassays and reverse transcription polymerase chain reaction (RT-PCR) tests. They’ll use these to test stool or vomit samples. These tests aren’t usually needed for individual cases, but can be helpful if there’s a norovirus outbreak.

It’s important to know that such tests have some limitations. Not every healthcare facility is able to carry out these tests, and the reliability can vary. The test results can also be affected by how many samples are tested, when the samples are collected, and how they’re handled.

There is another method called the Kaplan criteria that doctors use when lab tests aren’t available. This criteria is based on the following:

1. More than half of the people affected are vomiting.
2. Symptoms start 24 to 48 hours after exposure to the virus.
3. Illness lasts between 12 to 60 hours.
4. Tests show no bacterial infection in stool samples.

If all of these points are met, it’s highly likely there is a norovirus outbreak.

Treatment Options for Norovirus

When it comes to managing a norovirus infection, two main priorities are treating the patient’s symptoms and taking steps to reduce the chances of an outbreak. The primary clinical focus should be on making sure the patient is properly hydrated and trying to stop the disease from spreading to healthcare workers and those in close contact with the patient.

The best treatment often involves rehydrating the patient orally. The World Health Organization and the American Academy of Pediatrics recommend solutions that contain both electrolytes and glucose. These solutions are preferable to things like sports drinks and juices, especially for children, because they have a more accurate balance of components and don’t risk worsening diarrhea due to their high sugar content.

If the patient is vomiting uncontrollably or severely dehydrated, they may need to be hydrated via an IV and may require hospitalization. In general, antibiotics are not used unless there are signs of a bacterial infection. For adults, medication that slows the movement of the intestines (anti-motility agents) can be helpful, and medication to reduce nausea and vomiting (antiemetics) may provide relief from symptoms. Based on various studies, ondansetron can be helpful for children suffering from vomiting. However, it’s important to note that anti-motility agents aren’t advisable for pediatric patients.

When it comes to stopping a norovirus outbreak, measures like hand hygiene, cleaning surfaces, and avoiding exposure to body fluids are of paramount importance. Even as efforts to develop a vaccine for norovirus are underway, these measures remain essential.

Development of a vaccine is a high priority for both public health and economic reasons. As such, there are now several vaccines in various stages of development, with one even having completed Phase II adult clinical trials. Due to the virus being able to change and adapt over time, these vaccines are designed to target multiple strains of the virus, similar to the flu vaccine.

What else can Norovirus be?

When dealing with stomach problems, doctors need to examine all possibilities to understand what’s causing the issues. Some possible causes could be:

• Stomach infections like rotavirus, cholera or E. coli
• Infections in the digestive tract caused by salmonella or clostridium difficile bacteria
• A parasite called Cryptosporidium
• Enterovirus, a virus that causes different kinds of illnesses
• Shigella, bacteria that can cause severe diarrhea
• Other infections caused by Campylobacter or Vibrio bacteria

On the other hand, when a patient has abdominal pain, the doctor needs to consider whether it is caused by:

• Issues with blood flow in the intestines (mesenteric ischemia)
• A swelling or bulge in the large blood vessel that supplies the abdomen (abdominal aortic aneurysm)
• A hole in the wall of the stomach, small intestine, or large bowel (bowel perforation)
• A pregnancy that’s developing outside the uterus (ectopic pregnancy)
• Inflammation of the appendix (appendicitis)
• An inflammation of the gallbladder (cholecystitis)
• An obstruction or blockage in the bowel (bowel obstruction)
• Inflammation or infection of pockets in the wall of the colon (diverticulitis)
• An inflammation of the pancreas (pancreatitis)
• An infection in the kidney (pyelonephritis)
• A urinary tract infection
• Severe pain in the testes in men or ovary twisting in women (testicular or ovarian torsion)
• A heart attack (myocardial infarction)
• Pelvic inflammatory disease (PID), an infection in the womb and nearby parts in women

What to expect with Norovirus

Although most people experiencing a norovirus infection don’t face major complications, the virus is still responsible for over 70,000 hospitalizations and 800 deaths in the United States each year. People most likely to face severe consequences from norovirus infection are those at the very young or very old age range and those with a weakened immune system.

Specifically, newborn babies with this infection may develop a dangerous intestinal condition called necrotizing enterocolitis. Moreover, the elderly are shown to have a higher death rate from norovirus infection. Also, people with weakened immune systems can experience a more severe and extended illness, with symptoms like diarrhea that can last from several months to even years in some cases.

Possible Complications When Diagnosed with Norovirus

Common Issues:

• Low potassium levels in blood (Hypokalemia)
• Lack of adequate body fluids (Dehydration)
• Low sodium levels in blood (Hyponatremia)
• An imbalance in the body’s pH levels causing it to be overly alkaline (Metabolic alkalosis)
• Failure of kidneys to filter toxins from the body properly (Renal failure)
• A condition causing destruction of blood cells and kidney failure (Hemolytic uremic syndrome)

Preventing Norovirus

It’s important to maintain good hand and personal cleanliness habits. This involves washing your hands thoroughly and often, and keeping yourself clean in general. These simple practices can help prevent the spread of diseases and infections.