MadSci Network: Microbiology

Re: How are bacteria and diseases transmitted from place to place in a school setting?

Date: Mon Dec 15 18:18:38 2003
Posted By: June M. Wingert , RM (NRM) ,Associate Scientist
Area of science: Microbiology
ID: 1068159767.Mi

Greetings Jenni,
The following is an excellent article by Yvonne Potucek.
The article will give you insight on how to avoid catching something at 
You can also do a web search, type in How are bacteria and diseases 
transmitted and you will come up with a tremendous number of sites you can 
At the end of the article you will find a series of references that you 
could use to search even more in your Public Library.
The common cold is a disease caused by over 200 different RNA viruses 
(1,3,4,6,7,10,13).  Cold viruses are as mobile as their host, and similar 
viruses can be found in both hemispheres (in temperate and tropical 
climates).  Although the viruses are not very contagious (in laboratory 
experiments it has proved remarkably difficult to spread infection from 
one person to another), there are few humans who do not suffer at least 
one cold infection every year; many people suffer multiple infections 
(6).  There are currently no statistics readily available on worldwide 
common cold infections.  

The common cold is the most frequent infection of all age groups in the 
United States (4); according to the National Institute of Allergy and 
Infectious Diseases, Americans suffer approximately 1 billion colds each 
year (6,13,15). It has been estimated that, annually, infants and children 
suffer four to eight colds while adults suffer two to five colds 
(1,6,7,12).   Young children represent the main reservoir of common cold 
viruses.  Children suffer >from more colds than adults because they more 
easily encounter cold viruses for which they have not yet built 
antibodies.  Adults with regular contact with children are likely to have 
more common cold infections. (6,13)  

Cold viruses are not usually spread through contact such as kissing (6).  
Instead, they can be spread through large mucus particles expelled by 
close range coughs and sneezes (3,6,10).  The droplets in a sneeze can 
travel as fast as one hundred fifty feet per second and can reach 
distances of twelve feet (12).  Fingers and hands are often involved with 
the contamination process of both themselves and other surfaces.  Both 
consciously and unconsciously, humans frequently touch their eyes and 
nose.  This habit allows the cold virus to be easily transported both to 
and from its main place of replication, the nose (door handles in public 
places can contain a multitude of cold viruses) (3,6,10).  Contamination 
of the eyes can lead to infection of the nose because tears from the eye 
drain via a duct into the nasal cavity.  For infection to occur, it is 
critical that the viruses attach to the nasal cell lining of the nose 
(13).  As few as ten cold virons may be enough to cause infection (12).  

Despite the common belief, there is no evidence that the chilling of the 
body increases susceptibility to infection from cold viruses(2,6,13).  Nor 
does it increase the severity of symptoms. The connection may be made 
because the cooling of the skin and nose can cause sneezing, an early 
symptom of the cold.  (6)

The highest transmission of cold viruses occur during fall and winter 
months.  During these months the spread of infection is facilitated by 
greater periods of time spent indoors in poorly ventilated homes and 
offices (4,6).  Hot, dry air from heating systems can dry out nose and 
throat tissues, reducing the body‚s initial natural defenses against the 
cold viruses (4).  Ultraviolet light, which is known to kill viruses, is 
scarcer during the winter months.  (6)

Factors, such as stress, which influence immune response, may determine 
whether a person suffers from cold symptoms (1,2,6,8,12).  There is 
extensive evidence which indicates that every day stress can influence a 
person‚s susceptibility to infection.The start of school and college terms 
often coincide with an increased incidence of cold infections; a decline 
in the incidence of infections occur during half term periods and summer 
vacation. Experiments in which the common cold virus has been administered 
into the noses of healthy volunteers show that there is a link between 
recent history of psychological stress and susceptibility to infection.  
It is believed that the immune system is affected by the increased levels 
of corticosteroid hormones that are associated with stress (corticosteroid 
hormones are known to decrease resistance to infection) (6)  

Humans only recognize a fraction of infections caused by cold viruses.  
The majority of infections by cold viruses produce no disease and are 
Œsubclinical‚, despite extensive viral replication.  Other encounters with 
cold viruses go unrecognized because only minor symptoms, such as short 
lived throat irritation and a couple of sneezes, are experienced. (6) 

A cold virus‚ incubation period starts approximately two days before 
symptoms begin (6).   The first symptom of a cold is usually a dry, 
scratchy, sore throat.  Early signs of infection also include sneezing and 
a clear watery nasal fluid (3,6,10).  Of all symptoms, a blocked and 
stuffy nose can be considered the most bothersome.  Nasal congestion is 
caused by the swelling of large veins in the lining of nasal passages.  
The degree of vein swelling is controlled by nerves which release 
norepinephrine or noradrenaline.  Topical and oral nasal decongestants 
used to treat cold symptoms mimic the action of norepinephrine (6).  Fever 
is uncommon in adults, but frequently occurs in infants and the elderly 
(2,3,6,12).  Headaches, muscle aches and decreased appetite, more often 
associated with influenza, can also occur (3,10,6).  Coughing is usually a 
later symptom of the common cold and is caused by the inflammation and 
infection of the larynx, trachea and lower airways.  The cough can consist 
of either a dry, non-productive cough (indicative of inflammation of upper 
airways) or a productive chesty cough (indicative of inflammation of lower 
airways) (6).  Most cold symptoms last between one to four days, with 
nasal congestion lasting a week or more (4,7,8).

Common cold infections do not cause visible damage to the lining of the 
nose.  Sites of infection can occur as tiny pin points scattered over the 
lining of the nose and throat.  The oxidizing agent produced by white 
blood cells in response to infection is what causes actual damage to the 
cells in the nasal lining (and thus symptoms) (6).  The cold symptoms 
themselves are caused by the effects of a complex soup of chemical 
mediators acting on blood vessels, glands, and nervous tissue; these 
mediators include: bradykinin, prostaglandins, tachykinins, histamine and 
cytokines (6,8).  Of these mediators, bradykinin is proposed to play a 
major role in the occurrence of symptoms.  In experiments, the intranasal 
administration of bradykinin in healthy volunteers caused nasal congestion 
and irritation, stimulation of nasal secretion and throat irritation.  
Some interest has been shown in developing a medication which would act as 
a bradykinin inhibitor.  If such a medication is developed, the research 
would most likely come from experiments with medications for the treatment 
of rheumatoid arthritis (bradykinin is also implicated in causing the pain 
and swelling associated with joint inflammation). (6)

Because all cold viruses exhibit similar symptoms, the nature of the cold 
virus cannot be identified by symptoms (6).  Colds can be caused by a wide 
variety of viruses such as: coronavirus, respiratory syncytial virus, 
adenovirus, parainfluenza virus, and influenza virus (6,10).  
Coronaviruses are believed to cause a large percentage of all adult colds 

The common cold has been researched since the first infection experiment 
in 1956 (8), but in-depth discovery of the structure of cold viruses did 
not occur until the last twenty years.  Michael Rossman was the first 
person to view the topography of not just the rhinovirus, but of any human 
virus.  In a four year project ending in 1985, Michael Rossmann was able 
to piece together an accurate three-dimensional model of Rhinovirus 14 by 
creating a virus crystal (10,14).  "Because the millions of viruses in 
each crystal were virtually identical and all oriented in precisely the 
same direction, information gleaned from the entire crystal could be used 
to delineate the form of a single virus."  To produce an atomic map of the 
virus, Rossmann and his colleagues bombarded hundreds of crystals with 
extremely thin x-rays from the Comell High Energy Synchrotron Source.  The 
x-rays were reflected onto sheets of film as dots, which were then 
deciphered into patterns by computer. Looking over the "maps" of 
Rhinovirus 14, Rossmann and his colleagues discovered that its shell was 
made up of four recurring proteins that formed protrusions and 
depressions.  They also discovered that these "mountains" varied from one 
generation of virus to the next, so that our antibodies cannot 
consistently recognize them.  From his research on the structure of the 
Rhinovirus, Rossmann was able to conclude that the viral attachment site 
of Rhinoviruses is hidden in its "valleys" and "canyons".  Scientists 
consider this a viable explanation on how the cold virus is able to fool 
our antibodies into believing that it is nonthreatening. (10)  

Rhinoviruses, or nose viruses, are responsible for thirty to forty percent 
of all adult colds (6,10).  There are more than 100 different rhinoviruses 
identified today (10,12).  Rhinoviruses are of the family Picornaviridae 
(11) and isosahedral in shape with a diameter measurement of approximately 
20 nanometers (6,10).  Rhinoviruses have no envelope, are smooth and 
spherical in appearance (in electron micrographs), and have an angstrom of 
approximately 140.  They are unstable below a pH of 5-6 and have a density 
in CsCl of 1.38-1.42 g/ml (11).  Protein shell depressions, or Œcanyons‚, 
allow the Rhinovirus to fit onto cell surface protein receptors, enter the 
cell and uncoat to release its strand of genetic code (6).  The majority 
of human Rhinoviruses recognize ICAM-1 (inter-cellular adhesion protein) 
cell receptors, but a small number Rhinoviruses may recognize LDL (low-
density lipoprotein) cell receptors (11).  Rhinoviruses grow best at 
temperatures of 33 degrees Celsius, the temperature of the human nasal 
mucosa (13) 

Research on the common cold is often limited by a variety of factors.  
Some viruses, such as the Rhinovirus, limit testing because they only 
produce symptoms in humans (10,12).  Permission for human testing is 
difficult to receive without prior animal testing.  Like any other 
research project, the funding required to support experimentation is 
great.  Research projects are in part motivated by the billion dollar 
industry that a cure for the common cold would create.  Unfortunately, 
most of the research done has provided cures that have produced 
unacceptable side effects (side effects that are more damaging that the 
virus itself). (12)

Michael Rossmann and his colleague, Tom Smith, have been testing a series 
of compounds in hopes of finding one that prevents colds by paralyzing the 
virus in the cell.  "These drugs sink into the canyon and then pass 
through a 'pore' into a cavity below the canyon floor."  Researchers 
suspect that the virus‚ cavities add to the flexibility of the virus‚ 
structure; by filling in the cavity, the drugs would stiffen the virus and 
lock its surface so that it could not disassemble and release its genetic 
material to reproduce. (10)

Richard Colonno of Merck Sharp & Dohme Research Laboratories has focused 
on viral target cells in the nose.  Colonno began by testing twenty four 
rhinoviruses, and projected that almost ninety percent of all rhinoviruses 
bind to the same receptor.  Through culturing experiments, Colonno 
discovered an antibody that, in human studies, delayed the occurrence of 
symptoms and reduced their severity.  Colonno's lab is now looking for a 
structure on the cell‚s protruding receptors (the sites that interact with 
the attachment points of both the virus and antibody) that corresponds 
with the infection site of the Rhinovirus to determine how it enters the 
cell. (10,12)

Two teams of scientists, Timothy Springer and Steven Marlin, and Jeffrey 
Greve and Alan McClelland, have produced a form of ICAM-1 that is soluble 
and free floating (it is not rooted in the cell ways).  This solution 
could be squirted into the noses of potential common cold victims in hope 
that the rhinovirus would snatch up the free-floating ICAM-1 and never get 
to the ICAM-1 receptors that lead into the cell.  There have been two 
trials of the nose spray which have produced a reduced infection rate and 
severity of symptoms.  The ICAM-1 nasal spray is still in trial stages. 

Gwaltney of the University of Virginia recently showed that the dabbing of 
the hands with a virus-killing iodine solution prevents transmission and 
self-inoculation; it can reduce the incidence of colds by as much as forty 
percent.  He is currently testing a new disinfectant hand lotion that‚s 
less harsh than iodine and doesn‚t stain the skin brown.(10) 

Elliot Dick of the University of Wisconsin has experimented with viricidal 
tissues (Killer Kleenexes).  He claims that these tissues prevent the 
spread of colds by catching and killing viruses before they escape into 
the air.  He also plans to test air-filtering systems that suck virus-
contaminated air away from healthy people and circulate fresh air in its 
place. (10) 

AG708 is an inhaled 3C-protease inhibitor which, in vitro, has been shown 
to be effective against 48 different serotypes.  Although AG7088 did not 
prevent rhinovirus infection in humans, it did moderate illness severity 
and is associated with a reduction of viral shedding.  Additional clinical 
investigations are currently ongoing. (9)

Pleconaril is an oral agent which has been shown to inhibit ninety percent 
of human rhinovirus serotypes in vitro.  In human subjects, Pleconaril has 
shown significant decreases in viral shedding.  Clinical investigations 
are currently ongoing. (9)  

Common colds are the leading cause of physician visits in the United 
States (1,13).  One of the best means of prevention is hand washing 
because it reduces the chance of viruses reaching the eyes and nose 
(1,3,6).  Research has been done on the effects of vitamin C, zinc, and 
echinacea, but experiments have exhibited contradictory results (1,15).  A 
variety of less researched alternatives are also available.  These 
include: homeopathy, hydrotherapy, acupressure, and aromatherapy (5).  

Viral infections are notoriously difficult to cure, and there are no 
scientifically proven medications which prevent a cold.  The main 
prevention  of viral infection, in general, is vaccination; this is 
impractical for cold viruses because of the great quantity of different 
viruses. (10)  

The common cold cannot be treated, but its symptoms can.  The following is 
a list of substances that can treat specific symptoms (2,3,5):

Stuffiness and nasal congestion: pseudoephedrine, phenylpropanolamine, 
Phenylephrine, oxymetazoline.

pain: ibuprofen, acetaminophen, aspirin Caffeine is sometimes included to 
boost the pain reliever's effectiveness; caffeine's ability to do this is 

clear drainage: diphenhydramin, chlorpheniramine, antihistamines (such as 
diphenhydramine or clemastine), decongestants (such as pseudoephedrine and 

cough: dextromethorphan

Common colds can be mistaken for allergies or bacterial infections, and in 
these cases antibiotics are often prescribed.  Prescription drugs do 
nothing to kill a cold virus (2,5).  Approximately sixty percent of the 
people who go to the doctor's office with a common cold receive 
antibiotics (12).     

1.  Applegate, Liz.  Fighting the Common Cold.  Copyrighted by OnHealth 
Network Company, 2000. Website.  Available at:
olumnist/item,76176.asp Accessed: 4 May 2000.

2.  Casano, Peter.  The Common Cold.  No Date Posted.  The Sinus Care 
Center Website.  Available at: Accessed: 
4 May 2000.

3.  Colds.  20 April 2000.  Copyrighted by, Inc.,2000. Website.  Available at:
id=children‚s+health&filename=568.htm Accessed: 4 May 2000.

4.  Common Cold.  July 1998. Copyrighted by OnHealth Network Company, 
2000. Website.  Available 
at:http://onhealt,275.asp Accessed: 4 May 2000.

5.  Common Cold.  No Date Posted. Website.  Available at: Accessed: 4 
May 2000

6.  General Common Cold Information.  19 July 1999.  Available 
at: Accessed: 4 May 2000.

7.  Greene, Alan.  What is the Difference Between a Cold and the Flu?.  5 
October 1998.  Dr.Greene‚s HouseCalls Website.  Available at: 
Accessed: 4 May 2000.

8.  Griffin, Marie R.  "Understanding Pathogenesis to Build a Better 
Mousetrap" from Second International Symposium on Influenza and Other 
Respiratory Viruses, Day 2- 11 December 1999.  Copyrighted by Medscape 
Inc., 1994-2000.  Medscape Website. Available at: 
Accessed: 4 May 2000.

9.  Kaiser, Laurent.  „New Drugs for Runny Noses‰ >from Second 
International Symposium on Influenza and Other Respiratory Viruses, Day 3 
ˆ 12 December 1999.   Copyrighted by Medscape Inc., 1994-2000.  Medscape 
Website.  Available at: 
Accessed: 4 May 2000.

10.  Radetsky, Peter.  Taming the Wily Rhinovirus.  No Date Posted.  
Available at: 
Accessed: 4 May 2000.

11.  Smith, Thomas J.  Rhinoviruses.  1 July 1996.  Available at: Accessed: 4 May 2000.

12.  Taubes, Gary.  "The Cold Warriors."  Discover Feb. 1999: pgs 40-50.

13.  The Common Cold (Fact Sheet).  May 1998.  National Institute of 
Allegy and Infectious Diseases Website.  Available at:
sheets/cold.htm Accessed: 4 May 2000.

14.  Viruses: From Structure to Biology.  No Date Posted.  Available at: Accessed: 4 May 2000.

15.  Wonznicki, Katrina.  Comparing Three Popular Cold Remedies.  
Copyrighted by OnHealth Network Company, 2000.  OnHealth Website.Available 
depth/item/item,33412_1_1.asp Accessed: 4 May 2000.

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