Matinum

Taking Charge of Your Health


Learning medicine is hard work! Osmosis makes it easy. It takes your lectures and notes to create
a personalized study plan with exclusive videos, practice questions and flashcards, and so
much more. Try it free today! 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.

Leave a Reply

Your email address will not be published. Required fields are marked *