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Norovirus – causes, symptoms, diagnosis, treatment, pathology


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much more. Try it free today! You’ve probably had the stomach flu, at
least once, right? Chances are, it was due to norovirus, which
is one of the most common causes of viral gastroenteritis. Sometimes it’s also called the Norwalk virus,
after the town in Ohio where a big outbreak in 1968 allowed scientists to isolate the
virus. There are several genogroups of norovirus,
but only groups I, II, and IV can cause disease in humans. Norovirus is part of the caliciviridae family
of viruses. They are naked viruses surrounded by an icosahedral
capsid, which is a spherical protein shell made up of 20 equilateral triangular faces. And they’re “naked” because the capsid
isn’t covered by a lipid membrane. They’re also single strand RNA viruses. This means that their RNA is actually mRNA
– and the host cell ribosomes use this mRNA to make one long polyprotein chain, which
is then broken into smaller pieces by viral proteases. This all happens in the cytoplasm of the host
cell, since that’s where ribosomes are found, and results in several viral proteins. The exact role of each specific viral protein
is still a bit of a mystery, but we do know that they mainly affect the small intestine. The small intestine has lots of tiny ridges
and grooves, each of which projects little finger-like fibers called villi. And in turn, each villus is covered in teeny
tiny little microvilli. This is called the brush border. All of this gives the small intestines plenty
of surface area to absorb nutrients. Norovirus blunts the villi and shortens microvilli,
and this disrupts the ability of the brush border to absorb certain nutrients, specifically
fat and a simple sugar called D-xylose. It also lowers the activity of alkaline phosphatase
and trehalase, which are digestive enzymes produced by brush border cells. Under a microscope, intestinal cells infected
by Norovirus have an intact mucosa and epithelium, but there are a lot of lymphocytes in the
lamina propria layer of the mucosa. Intercellular spaces are also larger, because
tight junction proteins that keep the cells together are damaged. Norovirus is very contagious and it’s primarily
transmitted from person to person via the fecal-oral route. In other words, you catch it by ingesting
stool particles of someone who is sick. This can happen if infected stool ends up
in the water supply or on agricultural fields, if flies land on it, and transfer stool particles
to other places, or by touching contaminated surfaces. You can summarize it as the four Fs: fluids,
fields, flies, and fingers. As a result, norovirus can end up in food
and drinking water, and is often spread via uncooked foods like leafy vegetables and shellfish. It can also be spread by droplets of vomit. The gist of it is, Norovirus spreads quickly
in close-quarter residence settings. This is why many cruise ships have made the
news because of norovirus outbreaks. Outbreaks are also common in nursing homes,
hospitals, schools, military barracks, athletic teams, and prisons. Ok, now symptoms usually show up after a 12
to 48 hour incubation period, and they last for 48 to 72 hours. They include acute onset, nonbloody vomiting,
which is linked to slower movement of food through the stomach, and watery diarrhea,
from the malabsorption of fat and D-xylose and decreased brush border enzymatic activity. There might also be abdominal pain, myalgia
– or muscle pain, headaches, and fever. Complications include chronic gastroenteritis,
which can happen in immunocompromised individuals, dehydration, and malnutrition. Some people may remain asymptomatic, but all
individuals who are infected with Norovirus can potentially shed the virus in their stool
for up to four weeks afterward. Diagnosis of norovirus infection can be done
with reverse transcriptase polymerase chain reaction, or RT-PCR, where a stool sample
is tested for viral RNA. Treatment for Norovirus is mostly supportive,
with oral rehydration or IV fluids. Additionally, antiemetics can be used to control
vomiting. Finally, there’s currently no vaccine for
norovirus. But preventive measures include proper water
and sanitation facilities, which block fecal-oral transmission by fluids, flies, and fields
– 3 of the 4 F’s. Hand washing with antiseptic soap and water
and sanitizing surfaces that would’ve come into contact with stool can prevent transmission
by fingers. Finally, it’s also recommended to avoid
close contact with people who have symptoms. All right, as a quick recap… Norovirus is a single-strand RNA virus from
the calicivirus family. It’s a very contagious cause of viral gastroenteritis
that is transmitted via the fecal-oral route, droplets of vomit, and contaminated food and
surfaces. It mainly affects the small intestine and
causes symptoms like acute onset vomiting and watery diarrhea. It’s usually self-limiting, with symptoms
disappearing within 48 to 72 hours. Since there’s no vaccine, the best prevention
for norovirus is proper handwashing, sanitizing surfaces, and having effective water and sanitation
facilities.

9 thoughts on “Norovirus – causes, symptoms, diagnosis, treatment, pathology

  1. My college suffered a norovirus outbreak several years ago. Around 200 students were affected by it. This video definitely clarified some lingering questions I had about norovirus. Thanks for the video!

  2. My fear!!!!!! Who else has a extreme fear of throwing up??? I'm having anxiety just watching this video.

  3. Norovirus is a mayor cause of death in third world countries! Especially among children and elderly.

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