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Rhinovirus - causes, symptoms, diagnosis, treatment, pathology

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Human Rhinovirus (HRV) is a communicable, infectious virus that causes inflammation

of the nasal mucosa, or rhinitis.

It mainly causes upper respiratory tract infections, and gets its rhino- name, meaning nose, because

it commonly causes a runny nose, nasal congestion, and sneezing, as well as a sore throat and

cough.

There are over 100 serologic known types and all of them can cause a "common cold” in

humans!

Now, rhinovirus belongs to the picornaviridae family of viruses.

They are naked viruses, about 30 nanometers in diameter, and they’re 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-stranded, positive-sense ribonucleic acid, or RNA, viruses.

This means that their RNA is actually mRNA, which the host cell ribosomes use to make

viral proteins.

Unlike other picornaviruses, rhinoviruses are acid labile.

That means they can be destroyed by stomach acid, so they don’t typically infect the

GI tract and don’t spread through a fecal-to-oral route.

On the other hand, rhinoviruses commonly infect the epithelium of the respiratory mucosa,

which lines the nasal cavity.

So rhinovirus transmission occurs through contact with infected respiratory secretions,

like snot and aerosols, particularly from nose blowing or sneezing.

Touching an infected surface, like a door handle or shaking hands, and then touching

an uninfected respiratory mucosa is a main way to transfer an infection - that’s because

rhinoviruses can survive up to 2 hours on the skin, and 4 days on surfaces.

Once rhinovirus has been introduced to the respiratory mucosa, it targets cell surface

receptors expressed at the surface of nasal epithelial cells.

Rhinoviruses can target a few specific receptors for entry, but one in particular is intercellular

adhesion molecule-1, or ICAM-1.

This attachment allows for rhinovirus to be eaten, or endocytosed, into the host cell.

During the endocytosis process, the icosahedral capsid breaks open, allowing the single stranded

RNA of Rhinovirus to gain access to the host cell cytoplasm.

In the cytoplasm, the host cell ribosomes take over viral protein production, helping

the virus replicate.

Now, when the host cell realizes it’s been infected, it releases proinflammatory proteins,

like cytokines and chemokines, to activate and attract immune cells to the site of infection,

and recruit even more immune cells from blood vessels in the lamina propria, the layer just

under the epithelium in the respiratory mucosa.

And the end result is local inflammation.

Rhinovirus infections can occur in any individual, but there are some groups who are more susceptible,

like young children, the elderly, and individuals who are immunocompromised, or have underlying

respiratory diseases like chronic obstructive pulmonary disease, asthma, or cystic fibrosis.

The symptoms of a rhinovirus infection are actually those often associated with the “common

cold”.

Symptoms usually begin about 1 to 2 days after infection, and can last for about 2 weeks.

And typically, they include nasal congestion and irritation, which can mean a runny nose;

sneezing; pressure in the head that results in headaches, or sinus, ear or facial pressure;

or a loss of smell and taste.

But can also include fatigue, malaise, or loss of appetite; and other symptoms of an

upper respiratory infection like a sore or irritated throat; a cough; or hoarseness.

And while symptoms are usually mild, factors like age, immunocompromised states, and underlying

respiratory diseases can result in much more drastic, and sometimes even more complicated,

life-threatening symptoms.

Rhinovirus is mainly diagnosed clinically; especially when “common cold” symptoms

are present without additional complications, concerning physical findings, or relevant

medical history.

A definitive diagnosis can be made with PCR testing of cultures from nasal secretions

or washings, but this is typically only done in more complex cases, like if an individual

is immunocompromised or has an underlying respiratory disease.

Now, because rhinovirus infections tend to be mild and self-limited, treatment typically

centers on relieving symptoms and preventing other people from becoming infected.

So, common symptom relievers include rest, hydration, and age-appropriate over the counter

medications, like first generation antihistamines, NSAIDS, and nasal decongestants.

And general precautions should be taken to limit spreading the virus, including covering

coughs and sneezes, thorough hand-washing especially after nose blowing, and regular

disinfecting of surfaces.

Ok, so to recap: Rhinovirus is a type of picornavirus which is the leading cause of the common cold.

It infects the epithelium of the respiratory mucosa, typically through a nasal route of

transmission.

A consequence of the inflammatory response from immune cells leads to rhinitis and the

hallmark symptoms of the common cold, including runny nose, nasal congestion, and sneezing.

A clinical diagnosis is usually made and treatment tends to center on symptom relief and preventing

the spread of infection to others.