The Very Common Cold

 

 

Photo Credit – CDC PHIL

 

# 6396

 

 

Last Sunday I wrote about this week’s General Meeting of the American Society for Microbiology that was being held in San Francisco, and provided some links to live and archived webcasts (see Webcast: ASM Live San Francisco 2012).

 

As you might expect, a large number of scientific presentations have been made over the past few days - and we’ve seen a number of press releases highlighting that research - including the one that follows, on just how common the `common cold’ really is.

 

 

The surprise here is - that among college students tested over an 8 week period - asymptomatic infections led symptomatic infections by a factor of 4 to 1.

 

Which suggests that simply staying away from people with cold symptoms may not provide much in the way of protection against rhinoviruses, and makes common sense interventions - such as frequent handwashing - probably even more important.

 

A few excerpts from the release, but follow the link to read it in its entirety:

 

 

Asymptomatic rhinovirus infection outnumbers symptomatic infection 4 to 1 among university students

The common cold virus may be more common than previously thought in university students not reporting any symptoms. Rhinovirus, the virus responsible for the common cold was found at some point during an 8-week study period in an estimated 60% of university students that were asymptomatic. Researchers from Canada report their findings at the 2012 General Meeting of the American Society for Microbiology.

 

“A high occurrence of asymptomatic infections indicates that university students can spread infections to classmates, or individuals in the community without knowing they are infected,” says Andrea Granados of McMaster University in Hamilton, Ontario, a researcher on the study. The study was conducted at McMaster University and St. Joseph’s Healthcare in Hamilton, Ontario, Canada as part of the McFlu2 COLD3 clinical trial by Granados and colleagues Emma Goodall, Marek Smieja and James Mahony.

 

Rhinovirus, best known for causing the common cold can also cause bronchitis and trigger asthma attacks.

 

<SNIP details on how the study was done>

 

Based on these findings, the researchers estimate that as many as 60.5% of the asymptomatic student population was infected at some time with rhinovirus over an eight week study period.

 

They also used PCR to determine the viral load in symptomatic and asymptomatic students. Students with asymptomatic rhinovirus infections had significantly less virus than symptomatic infections. Decreased amounts of the virus may be responsible for the lack of symptoms, says Granados, however, larger studies are necessary to confirm this finding.

 

“In this study, we found that university students with rhinovirus infections who lacked symptoms outnumbered by a factor of 4 the number of infected students with symptoms. The virus particles can be spread by aerosols or direct contact with an asymptomatic individual. There is no treatment for the common cold; therefore, frequent hand-washing is important to prevent the spread of the common cold particularly in early fall,” says Granados.

 

 

It’s happened to all of us, I suppose. 

We come down with a cold, wrack our brains trying to remember coming in contact with someone with the sniffles - and come up with a blank - leaving us to wonder just where the heck we caught it.

 

Today’s study provides a plausible explanation.

 

Granted, those with asymptomatic infections showed lower viral loads than those displaying cold symptoms - suggesting that they may be less efficient spreaders of the virus – but we don’t have enough data to know how much of a viral load it takes to spread the virus.

 

The good news here, I suppose, is that we can sometimes (perhaps often) get one of the numerous rhinoviruses that circulate without necessarily enduring the misery of cold symptoms.

The bad news is, we may be spreading those cold viruses to others while looking, and feeling, perfectly healthy.

Study: HRV In Long-Term Care Facilities

 

 

# 4789

 

 

I’ve returned from my 5-day vacation, and given a couple of days of rest, I should be recovered from the experience.

 

Luckily, the tropics remain quiet, the pandemic continues to wind down (see Crofsblog  Branswell: WHO could declare end of H1N1 pandemic this week), and in the dead of summer H5N1 is producing little more than tiny blips of background noise.

While the news may be quiet, we continue to see a flood of research articles in the wake of the 2009 pandemic, giving us much to look at during these dog days of summer.

 

One such article, published ahead of print in the CDC’s EID Journal, is called Rhinovirus Outbreaks in Long-term Care Facilities, Ontario, Canada.

 

Thankfully, the research is more interesting than the title might suggest. 

 

But then, it would almost have to be . . .

 

For the layperson, respiratory infections are pretty much divided up into three broad categories; colds, influenzas, and pneumonias.

 

But in reality, the spectrum of common respiratory viruses is far more diverse and includes such pathogens as metapneumovirus, parainfluenzavirus, respiratory syncytial virus (RSV), any of the myriad Rhinoviruses (Common cold), and a number of varieties of adenovirus.

 

Last October, during the height of the fall wave of the H1N1 pandemic, I posted the following graphic on my blog.

 

 

Of the more than 10,000 samples submitted for testing during the 1st week of October 2009, more than 72% – almost 3/4ths –  came back negative for influenza.

 

Although testing may miss some cases (samples degrade, viral shedding at the time of sampling may have been low, etc), it is pretty obvious that a lot of flu-like illnesses are caused by something other than influenza.

 

And frankly, except for a few peak weeks every flu season, the percentage of samples testing positive for influenza A is usually less than 10%.  

 

Which is why doctors generally refer to ILIs, or Influenza-like Illnesses (or sometimes ARI Acute Respiratory Infection), when making a clinical diagnosis. 

 

Testing to find out exactly what kind of virus a patient may have is time consuming, expensive, and not usually justified.  By the time test results come back, most patients will have recovered.

 

But for research purposes, testing can reveal a great deal of information.  

 

And one of the things we are learning is that some of the `lesser’ respiratory viruses – even the ubiquitous Rhinovirus – can produce serious (and sometimes even fatal) illness.

 

Late last year, in a blog entitled When The `Flu’ Isn’t The Flu, I wrote about the discovery at the Children’s Hospital of Philadelphia of an unusually virulent (and possibly new) rhinovirus – essentially a common cold – that began hitting some children hard earlier this fall.

 

We turn to Reuter’s ace Health and Science Editor Maggie Fox for the details, in her article from last fall

 

Not just swine flu - new cold virus may lurk, too

Tue Nov 17, 2009 3:24pm EST

By Maggie Fox, Health and Science Editor

WASHINGTON (Reuters) - Runny nose, fever, cough, even pneumonia -- the symptoms sound like swine flu but children hospitalized at one U.S. hospital in fact had a rhinovirus, better known as a common cold virus, doctors said on Tuesday.

(Continue. . . )

 

Which sets the table for today’s research piece, which looks at the incidence of Rhinovirus among patients in long-term care facilities in Canada during the last half of 2009.

 

Some excerpts from the the study, then some discussion.

 

Rhinovirus Outbreaks in Long-term Care Facilities, Ontario, Canada

DOI: 10.3201/eid1609.100476

Longtin J, Marchand-Austin A, Winter A-L, Patel S, Eshaghi A, Jamieson F, et al. Rhinovirus outbreaks in long-term care facilities, Ontario, Canada. Emerg

Infect Dis. 2010 Sep; [Epub ahead of print]

Respiratory tract illnesses are a major cause of illness and death among elderly persons, especially those in long-term care facilities. Although the most commonly identified viruses have been influenza virus and respiratory syncytial virus (RSV) (1), human rhinovirus (HRV) is being increasingly associated with severe respiratory disease and outbreaks in these facilities (2–6).

Clinical diagnosis of HRV by immunofluorescence and virus culture has been difficult because these methods are unreliable (7,8). Moreover, because multiple serotypes of HRV exist, retrospective serologic testing cannot be used to evaluate the prevalence of HRV disease (5). As a result, the number of outbreaks caused by HRV in long-term care facilities, and the associated illness and death, may be substantially underestimated.

 

We therefore used 2009 surveillance data to estimate prevalence of HRV disease in long-term care facilities.

 

<SNIP>

 

<SNIP>

 

In conclusion, using data from a routine surveillance network, we found high prevalence of HRV during a period that encompassed the first and second waves of pandemic (H1N1) 2009. These findings are in accordance with the increasing knowledge that HRV outbreaks cause severe and fatal disease.

 

 

I’ve only excerpted some of the highlights. While only 4 pages long, the entire article is well worth reviewing.

 

Given the elderly demographics in most long-term care facilities, it isn’t terribly surprising that the impact of pandemic H1N1 was as low as is depicted here. Those born before about 1957 have shown varying levels of immunity to the virus.

 

But the big news here is the high prevalence of HRV (Human Rhinovirus) which comprised nearly 60% of the samples, and that these viruses were implicated in a number of deaths.

 

 

This research did not test for human bocavirus or influenza C virus, which the authors state could be involved in the outbreaks that had no identified cause.

Additionally, we’ve seen other research that has identified mixed infection - by more than one virus – in more than 10% of cases  (see ILI’s Aren’t Always The Flu).

 

All of which points out the complexity that this panoply of human respiratory pathogens represent. 

 

Rhinoviruses are not necessarily the burdensome, but relatively benign viruses, that most of us think of. 

 

Particularly among vulnerable populations, like children, the elderly, and the medically frail. 

 

Granted, pandemics never are a `good’ thing.  But they often spur advances in scientific research, and sometimes that leads us down surprising paths. 

 

While it is influenza that usually makes the headlines, developing  a better understanding of the impact of non-influenza ILI’s may eventually lead to better testing and treatments, which could end up saving lives down the road.

Enough To Make You ILI

 

 

# 4187

 

After hearing repeatedly that nearly 100% of all positive flu samples over the last six months have been the novel H1N1 virus, you might come away believing if you’ve had a flu-like illness you’ve had the pandemic virus.

 

The problem is, a crucial piece of information is missing; What percent of all samples tested positive for influenza?

 

And here, the answer may be surprising.  

 

At its height, during the pandemic wave back in late October, the percentage of samples from people with ILI’s (Influenza-like illnesses) submitted to the CDC that tested positive for influenza (any type) was under 40%.

 

You see, there are a plethora of respiratory pathogens that circulate year-round, and influenza makes up but a small percentage of them.

 

Some of the `usual suspects’ would include metapneumovirus, parainfluenzavirus, respiratory syncytial virus (RSV), adenovirus, or any of the myriad Rhinoviruses (Common cold).

 

Back in October, I looked at some of these other viruses in a blog entitled:

 

Tuesday, October 13, 2009

ILI’s Aren’t Always The Flu

 

# 3832

Although nearly all of the influenza circulating in the the US and Canada right now is apparently the novel H1N1 `swine’ flu, it would be incorrect to say that if you have a flu-like illness, you must have the pandemic flu.

 

Last week’s numbers from the CDC’s FluView, which I’ve plugged into the above spreadsheet so as to generate a graph, show that more than 72% – almost 3/4ths – of all virus samples tested from people who had flu-like symptoms came back negative for influenza.

 

 

For the latest reporting week (49), the CDC is showing just under 7% of the viruses sampled testing positive for the H1N1 virus.  Even though nearly 100% of the influenza detected has been H1N1.

 

 

 

Last night Maggie Fox, Reuter’s Health and Science Editor, brought us details of some new analysis of the other 94% of the viruses being tested in the US.  

 

Maggie is one of the best reporters in the business, and her work is always worth reading it in its entirety.

 

 

Other viruses abound in U.S. flu season, tests show

 

Maggie Fox, Health and Science Editor

WASHINGTON

Tue Dec 22, 2009 5:29pm EST

WASHINGTON (Reuters) - Several flu-like viruses are more common than usual this flu season in the United States, adding to the misery and confusion caused by H1N1 swine flu, one lab company said on Tuesday.

 

Kansas City, Missouri-based ViraCor Laboratories found that only 6 percent of the samples it was sent tested positive for influenza A virus. Tests by the U.S. Centers for Disease Control and Prevention show virtually all influenza now circulating is H1N1 swine flu.

 

The rest include a range of flu-like viruses, each caused by a distinct germ but all causing similar symptoms.

 

By far the most common is rhinovirus, one of the so-called common cold viruses, the testing company found.

 

This fits in with a report last November from Children's Hospital of Philadelphia, where 500 children were hospitalized with rhinovirus in September and October -- an unusually high number to be that sick with a normally mild virus.

(Continue . . . )

 

 

In mid-November, in a blog entitled When The `Flu’ Isn’t The Flu, I wrote about the discovery at the Children’s Hospital of Philadelphia of an unusually virulent (and possibly new) rhinovirus – essentially a common cold – that began hitting some children hard earlier this fall.

 

Once again, we turn to Maggie Fox for the details, in her article from a little over a month ago.

 

Not just swine flu - new cold virus may lurk, too

Tue Nov 17, 2009 3:24pm EST

By Maggie Fox, Health and Science Editor

 

WASHINGTON (Reuters) - Runny nose, fever, cough, even pneumonia -- the symptoms sound like swine flu but children hospitalized at one U.S. hospital in fact had a rhinovirus, better known as a common cold virus, doctors said on Tuesday.

 

Hundreds of children treated at Children's Hospital of Philadelphia had a rhinovirus, and federal health investigators are trying to find out if it was a new strain, and if this is going on elsewhere in the country.

 

(Continue. . . )

 

All of this means that if you’ve had an ILI in recent weeks there is a pretty good chance it was something other than novel H1N1. 

 

Doctors don’t generally test for anything beyond influenza when a patient comes in with a flu-like illness because the tests are expensive and the results aren’t generally available until after the virus has run its course.

 

In other words, they have very little bearing on treating a patient.

 

 

Surveillance and testing do have value from an epidemiological standpoint, however.  And so this data is of great interest to scientists, and to doctors, who use it to decide how prevalent various viruses are in their community.

 

If you’ve put off getting the H1N1 vaccine because you believe you’ve already  had the virus, you might want to reconsider that decision. 

 

You may have had something else entirely, and may not have immunity you might think you do. 

 

While many people who contract the H1N1 virus have a mild course of illness, not every `mild flu’ over the past 6 months has been due to the pandemic virus.

 

Something to bear in mind when someone recounts how mild the `pandemic virus’ was for them.  They may not realize it, but they may have had nothing more than a nasty cold.

Why They Call It COLD & Flu Season

 

 

# 4030

 

 

Last week in a blog entitled When The `Flu’ Isn’t The Flu, I wrote about a discovery at the Children’s Hospital of Philadelphia of an  unusually virulent (and possibly new) rhinovirus – essentially a common cold – that began hitting some children hard earlier this fall.

 

Even during the height of flu season, we know that other respiratory viruses are circulating, and probably making up half or more of all influenza-like-illnesses (ILIs).

 

These illnesses may range from common rhinoviruses to metapneumovirus, parainfluenzavirus, or respiratory syncytial virus (RSV), to one of the adenoviruses.

 

This chart (see ILI’s Aren’t Always The Flu) from early October show more than 70% of samples tested by the CDC came back negative for influenza.

 

 

Now Maggie Fox, Health and Science editor for Reuters, picks up the story with some more details.  Maggie always does terrific reporting, so follow the link to read it in its entirety.

 

 

Not just swine flu - new cold virus may lurk, too

Tue Nov 17, 2009 3:24pm EST

By Maggie Fox, Health and Science Editor

 

WASHINGTON (Reuters) - Runny nose, fever, cough, even pneumonia -- the symptoms sound like swine flu but children hospitalized at one U.S. hospital in fact had a rhinovirus, better known as a common cold virus, doctors said on Tuesday.

 

Hundreds of children treated at Children's Hospital of Philadelphia had a rhinovirus, and federal health investigators are trying to find out if it was a new strain, and if this is going on elsewhere in the country.

 

“What began to happen in early September is we started seeing more children coming to our emergency room with significant respiratory illness," said Dr. Susan Coffin, medical director of infection control and prevention at the hospital.

 

Doctors and parents assumed it was the new pandemic H1N1 swine flu, which would be expected to re-emerge as schools began in September. But it was not, Coffin said in a telephone interview.

(Continue . . . )

 

 

When The `Flu’ Isn’t The Flu

 

 

# 3997

 

A very interesting report this morning out of Philadelphia, where tests showed that as many as 40% of the people reporting to the ED (Emergency Department) of a local hospital in early fall with `the flu’ actually had a Rhinovirus instead.

 

With more than 100 different Rhinovira identified, these viruses – often referred to as  `the common cold’ – produce the majority of respiratory illness in the world. 

 

They normally take residence in our upper respiratory tract and can make us miserable for a week or more.

But according to doctors at Children's Hospital of Philadelphia, the strain of Rhinovirus circulating in Philadelphia this fall produced unusually severe symptoms:

 

Besides the sheer numbers of rhinovirus, Coffin was surprised that it was causing more problems - wheezing, pneumonia, fever, and lower-respiratory-tract infections - than are normally associated with the common cold, which typically infects the upper respiratory tract.

 

That has led her to suspect that a strain not seen here before may be responsible. The CDC's lab will attempt to identify the strain.

 

If all of this sounds vaguely familiar, it is because we recently discussed this very issue; the idea that not everyone who thinks they’ve had swine flu over the past 6 months really did.

 

Even during the height of flu season, at least half of all ILI’s (influenza-like-illnesses) are probably caused by something other than influenza.   Perhaps metapneumovirus, parainfluenzavirus, respiratory syncytial virus (RSV), one of the myriad Rhinoviruses (Common cold), or adenovirus.

 

This chart (see ILI’s Aren’t Always The Flu) from early October show more than 70% of samples tested by the CDC came back negative for influenza.

 

As I pointed out in October, the reason for bringing all of this up – besides the fact that it is interesting – is really two-fold.

 

First, since many of these milder ILI’s are commonly perceived by the public as being the `flu’, many people have a false perception of what having real influenza can be like.

That `mild swine flu’ infection last September, that convinced your family that this pandemic is much to do about nothing, may not have been swine flu after all.

 

And  second, it is entirely possible that some of the people who suspect that they’ve already had the pandemic virus over the summer or last spring – and would therefore be immune – really had one of the other commonly circulating respiratory viruses. 

Which means that they may not have acquired the protective antibodies they think they have.

Two things to consider, now that the H1N1 vaccine is becoming more widely available.

 

The article, of which I’ve just posted an excerpt, is well worth reading in its entirety.  

 

 

Posted on Thu, Nov. 12, 2009

Tests show fall outbreak is rhinovirus, not swine flu

By Don Sapatkin

Inquirer Staff Writer

I had swine flu. It is almost a badge of honor, suggesting that the speaker survived the first pandemic of the 21st century and is immune to the next wave.

 

It also may be wrong.

 

Tests at Children's Hospital of Philadelphia suggest that large numbers of people who got sick this fall actually fell victim to a sudden, unusually severe - and continuing - outbreak of rhinovirus, better known as a key cause of the common cold.

 

Experts say it is logistically and financially impossible to test everyone with flulike symptoms. And signs, treatment, and prognoses for a bad cold and a mild flu are virtually identical, so the response hardly differs.

 

But the finding may send an important message to parents who (despite doctors' recommendations) are questioning the need to immunize their children against swine flu because they seemed to have already had the disease, said Susan Coffin, director of infection prevention and control at Children's Hospital.

 

"Maybe their child is still susceptible to H1N1 and should still get the vaccine," Coffin said.

 

For years, rhinoviruses have been the Rodney Dangerfields of microbes. Even major institutions have found plenty of reasons not to pay them much mind. They are exceedingly common, they cause mere colds, they come in hundreds of hard-to-identify strains that make testing a challenge, and there is no effective treatment anyway.

 

Neither the federal government nor the states track rhinoviruses in the way they do "surveillance" for influenza, based on samplings of doctor diagnoses, emergency-room visits, and lab reports. Children's Hospital of Philadelphia is one of the few institutions that routinely checks for them whenever it tests for influenza and other viruses.

 

(Continue . . . )