#11 - Rhinoviruses: One of the Most Common Viral Infections Explained

00:00:07: These virus infections are very, very common.

00:00:10: In fact approximately fifty percent of all common colds are caused by rhinoviruses.

00:00:33: Viralogical.

00:00:35: with Florian Kramer.

00:00:47: Welcome to this week's episode of Virological!

00:00:50: This episode was recorded on January eighteenth of twenty-twenty six in Vienna and we're going talk about a virus infection that all of us already had probably multiple times.

00:01:04: It's an upper respiratory tract infection that is caused by rhinoviruses, just about the name.

00:01:11: Rhino basically comes from ancient Greek and means From the nose or off-the-nose.

00:01:18: so we're dealing with a virus here that infects the nose, infects their upper respiratory trach.

00:01:23: actually we are dealing with whole bunch of different viruses.

00:01:27: as you will see Rhinoviruses are part of the bicornoviruses, so it's related to bolio and It belongs to the genus of enteroviruses.

00:01:40: These viruses are positive strand RNA viruses.

00:01:45: They don't have a lipid envelope.

00:01:47: they're about twenty four to thirty nanometer in diameter So pretty small And they have four structural proteins that form the shell or the envelope And they're called VP-I, so viral protein I. Viral protein II, viral protein III and viral protein IV.

00:02:07: They form a symmetric structure... ...and there are actually exactly sixty copies of each of these proteins in the virus particle.

00:02:15: As i mentioned it's whole group of viruses that is pretty diverse.

00:02:19: We have three different types.

00:02:21: we've human rhinovirus A, human rhinavirus B.. ..and human rhinovirus C And within these groups, there's a lot of diversity in terms of serotypes.

00:02:32: In the human rhinoviruses A we have about eighty different viruses.

00:02:38: For B We've got thirty different viruses and for C we'll get fifty different viruses.

00:02:44: So really humongous diversity!

00:02:47: These viruses also use different surface proteins on our cells to attach them into their cells.

00:02:54: Human rhinoviruses A & B mostly use protein that's called ICAM-I.

00:02:59: That is an integrin on the surface of our cells, so about ninety percent of A&B rhinoviruses used it and ten per cent of A & B rhinovirus uses LDL receptor.

00:03:13: So basically this is a LDL cholesterol receptor.

00:03:17: Rhinovirus C uses CDHR-III, which is a catarine, so that's a different protein or different receptor.

00:03:26: A little bit about history here.

00:03:28: The virus was first isolated or rhino viruses were first isolated in nineteen fifty six by Winston Price at Johns Hopkins University in Baltimore.

00:03:39: he isolated the virus from a group of nurses that had mild upper respiratory tract infection and He called the virus jh virus.

00:03:48: so for John's Hopkins basically In nineteen eighty-five, the structure of the virus was solved using X-ray crystallography.

00:03:57: That was done by a team from Purdue University and University of Wisconsin led by Michael Rosman until two thousand six we only had human rhinovirus A and human Rhinovires B And in two thousand Six Human Rhinovarious C Was discovered in New York and Australia.

00:04:16: So little bit about Illness and the symptoms that a virus infection can cause.

00:04:22: First of all, how you get infected?

00:04:25: There's multiple ways.

00:04:26: the virus can be transmitted via aerosols so these are just really tiny little droplets which stay in air for long time.

00:04:34: It also could be transmitted by larger respiratory droplets but also by fomites meaning via objects that are contaminated like cell phones, for example.

00:04:45: Or by direct contact with an infected person.

00:04:48: The reproductive number or R naught so the number tells you how many people and infected person will infect is about two point five.

00:04:58: So it means that rhinoviruses a little bit more infectious than influenza viruses For example which ever are not of about one point five But they're less infectious then currently circulating variants of South coronavirus too.

00:05:12: The incubation time is approximately two days, but it can be as short as twenty hours and as long as four days.

00:05:20: And when you get symptoms the typical symptoms are a runny nose or stuffed nose.

00:05:26: So typically common cold symptoms may be a sore throat A little bit of coughing so mostly they're upper airways that are involved.

00:05:34: Sometimes you also can have fatigue, headache maybe muscle pain or diarrhea but that's relatively rare and in very rare cases people get fever.

00:05:45: But again if we have a respiratory tract infection it is unlikely to be a rhinovirus.

00:05:53: These virus infections are very common.

00:05:55: In fact approximately fifty percent of all common colds are caused by rhinoviruses.

00:06:02: Typically in the northern hemisphere we have more circulation during the cold season from September to April, but it's not like rhinovirus.

00:06:11: infections stop during summer.

00:06:13: You can get infected during the summer as well – It is just not as common as during winter seasons!

00:06:21: It was also important mentioned that a lot of rhino virus infections are asymptomatic.

00:06:25: The assumption is that in kids about fifteen-thirty percent of the infection are asymptomatic and fifty percent of the infections are asymptomatic in adults.

00:06:36: Once you had an infection with a specific rhinovirus, You actually make neutralizing antibodies that can protect your from reinfection but the problem is they're very specific to that strain that infected you.

00:06:47: We've heard there's more than one hundred fifty different strains so unfortunately immunity doesn't protect it from other strains.

00:06:55: So if we get exposed another strain will get infected again.

00:07:00: I already mentioned that these viruses usually cause upper respiratory tract infections, they are relatively mild.

00:07:07: One reason for it is this virus grows at low temperature.

00:07:12: They prefer thirty-three to thirty five degree Celsius and don't grow well at thirty seven degrees Celsius.

00:07:18: And basically means the kind of restricts in most cases up by airways where its called a right.

00:07:24: if you go down deep into the lung The temperature gets higher and they basically restricts their growth.

00:07:31: And that might be one of the reasons why most of these infections are mild, but there can also be more severe infection specifically with Rhinovirus A and Human Rhinoviruses C. Typically human rhinovires B infections are very mild.

00:07:51: The more severe forms of the rhino virus infections occur typically in small children or babies at a very old age people and in people who have a compromised immune system.

00:08:03: And, some cases this can lead to bronchiolitis or even do pneumonia.

00:08:11: just explain it little what bronchiolis means.

00:08:15: where the bronchiols are so typically our airways.

00:08:19: we have bronchus which kind of is bigger airways the alveoli, it's like little bubbles where the gas exchange between blood and air happens.

00:08:32: And there are small airways that connect to alveolus and bronchialis.

00:08:40: They're very thin!

00:08:42: If you get infections during this can happen with human rhinovirus.

00:08:46: then you have issues breathing which is more severe.

00:08:51: What also should be mentioned.

00:08:53: Rhinoviruses often co-infect people with other viruses, but also with bacteria.

00:08:59: And that can contribute to more severe infections and I think it should be mentioned.

00:09:08: before the pandemic nobody tested for rhinoviruse.

00:09:13: Now there's a lot of testing where you test a number of respiratory viruses at the same time.

00:09:22: Sometimes in more severe infections, rhinovirus is involved too and that hasn't been reported much before the pandemic just because there was less testing.

00:09:33: I think i also should mention that there's an association between rhino virus infections and asthma And There can be two associations.

00:09:44: The first one it seems that rhino-virus infection can actually set up people to get asthma later on.

00:09:52: that often happens when babies, for example very small children.

00:09:57: I have more severe infections with rhinoviruses where the virus reaches these bronchioles and then this kids has a higher risk of getting asthma later in life.

00:10:09: And it seems that in terms of virus infections Rhinovirus infections are second most cause of Asthma after RSV.

00:10:18: so RSV is another respiratory virus.

00:10:21: thats known for setting people up to get asthma later in life.

00:10:26: And then there's another association, which is that if somebody already has asthma and gets a rhinovirus infection the infection can exacerbate their asthma quite a bit.

00:10:36: so it could be highly problematic too.

00:10:39: So what you do about rhino virus infections?

00:10:43: The truth is not much.

00:10:44: There are no vaccines, there's some vaccine development but it isn't very far and its really hard to make vaccines against rhinoviruses because they're so diverse depending on different receptors And most of the immunity that you get is really strange specific.

00:11:01: So it's really hard making vaccines which would work with all these diversity or rhinoviruses maybe even harder than making a universal flu vaccine and that's why vaccine development is not that far.

00:11:14: And so far we also don't have any kind of antivirals, they really work well against rhinoviruses.

00:11:20: So basically if you get an infection there isn't much to do about it other than write them out.

00:11:26: There actually aren't many things in terms of preventing the infection except for distancing maybe masking or washing your hands etc.

00:11:34: Of course, because these virus infections are relatively mild and relatively harmless in most cases.

00:11:43: These viruses also haven't been prioritized for vaccine development and for antiviral development.

00:11:51: So to summarize all of this rhinoviruses a very diverse group of viruses that cause many many infections Very common infections That are often mild And even though they are annoying, They're not very dangerous.

00:12:07: But in some cases it can also lead to bigger problems and even fatalities have been recorded with rhinoviruses but again tons of infections most of them harmless and mild.

00:12:18: That's it for today for virological.

00:12:21: I just wanted to mention if you have any comments or suggestions Or questions.

00:12:26: please feel free write an email to Virological at www.podcastwerkstatt.com And at some point we'll have an episode where we answer questions and comments that came in.

00:12:39: Thanks for listening, until next week!

00:13:18: Bye!