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Learning objectives

  • Describe the different types of disease reservoirs
  • Compare contact, vector, and vehicle modes of transmission
  • Identify important disease vectors
  • Explain the prevalence of nosocomial infections

Understanding how infectious pathogens spread is critical to preventing infectious disease. Many pathogens require a living host to survive, while others may be able to persist in a dormant state outside of a living host. But having infected one host, all pathogens must also have a mechanism of transfer from one host to another or they will die when their host dies. Pathogens often have elaborate adaptations to exploit host biology, behavior, and ecology to live in and move between hosts. Hosts have evolved defenses against pathogens, but because their rates of evolution are typically slower than their pathogens (because their generation times are longer), hosts are usually at an evolutionary disadvantage. This section will explore where pathogens survive—both inside and outside hosts—and some of the many ways they move from one host to another.

Reservoirs and carriers

For pathogens to persist over long periods of time they require reservoir s where they normally reside. Reservoirs can be living organisms or nonliving sites. Nonliving reservoirs can include soil and water in the environment. These may naturally harbor the organism because it may grow in that environment. These environments may also become contaminated with pathogens in human feces, pathogens shed by intermediate hosts, or pathogens contained in the remains of intermediate hosts.

Pathogens may have mechanisms of dormancy or resilience that allow them to survive (but typically not to reproduce) for varying periods of time in nonliving environments. For example, Clostridium tetani survives in the soil and in the presence of oxygen as a resistant endospore. Although many viruses are soon destroyed once in contact with air, water, or other non-physiological conditions, certain types are capable of persisting outside of a living cell for varying amounts of time. For example, a study that looked at the ability of influenza viruses to infect a cell culture after varying amounts of time on a banknote showed survival times from 48 hours to 17 days, depending on how they were deposited on the banknote. Yves Thomas, Guido Vogel, Werner Wunderli, Patricia Suter, Mark Witschi, Daniel Koch, Caroline Tapparel, and Laurent Kaiser. “Survival of Influenza Virus on Banknotes.” Applied and Environmental Microbiology 74, no. 10 (2008): 3002–3007. On the other hand, cold-causing rhinoviruses are somewhat fragile, typically surviving less than a day outside of physiological fluids.

A human acting as a reservoir of a pathogen may or may not be capable of transmitting the pathogen, depending on the stage of infection and the pathogen. To help prevent the spread of disease among school children, the CDC has developed guidelines based on the risk of transmission during the course of the disease. For example, children with chickenpox are considered contagious for five days from the start of the rash, whereas children with most gastrointestinal illnesses should be kept home for 24 hours after the symptoms disappear.

Questions & Answers

what is microbiology
vijay Reply
microbiology is the scientific study of microorganisms .microorganisms are those organisms that are too small to see with the naked eye ex-bacteria fungi
Yashkin
a branch of biological science concerned with organisms that can not be observed with a naked eye
Mooya
what are the types of granulocytes and explain
lord
I want to know more about sample collection on the field
Ama Reply
blood collection and urinarysis
Lizzy
2143
Lizzy
yes
Lizzy
In the periodic table the number on the upper left hand side is what
Aurelia Reply
Hydrogen
Tob
am not talking about the elements
Aurelia
Is it the atomic number or the mass number
Aurelia
hologen
Usman
differences between acid fast and non acid fast bacilli
ANTHONY Reply
acid fast have cell wall that holds to carbol fuschin stain while non acid fast doesn't have. it readily releases out the primary stain the carbol fuschin.
LAFIA
where do I post a question that isn't related to that topic
eklectc
hi everyone
kennedy
hello
Olivia
for sure, this question is not related to the topic.
LAFIA
can someone explain the process of glycolysis and the electron transport chain? I'm so freakin lost. it loses carbons, gains hydroxyls, gains, loses Hydrogens....ugh it's like a foreign language to me! or direct me to a youTube video or something that will make this seem easier to concept?
eklectc
it's a loaded question, sorry!
eklectc
why is DNA a genetic material
Mcbeth Reply
DNA is genetic material because it contains chromosome contains the traits which includes characters and behavioral characteristics
chima
why is it difficulty to classfy protista
Tanaka
Good
Eddy
what is infection prevention
Muhammed Reply
good hygiene
Dhaqan
way of preventing disease causing germs
henry
maintenance of sterilization
Pooja
h
Faustina
describe the components of the epidemiology triangle
Muhammed Reply
Hai
Nantongo
hii
Md
where from you
Md
i am Indian
Md
you
Md
Hello friend
effiong
How are you people doing
effiong
أ‌) Host factor ب) pathogen ج) environment
Widad
Hello
Kofi
Hi
Widad
hey hi
kalai
The epidemiologic triangle is made up of three parts: agent, host and environment
Princess
please can a microbiologist will work at hospital
Usman
what are the fluids used in biochemistry Lab used to diagnose diseases
Jb Reply
fadumo qule a gemil3
fadumo Reply
Faadum mahamud disease micro biology
fadumo
makuway diinkaraan suaalo
fadumo
history of microbiology
Balqees Reply
Penicillin is caused by what microorganism
Balqees
Penicillin is caused by what microorganism
Balqees
penicillium notatum
Pooja
M sorry I mean penicillin is caused by what Fungi
Balqees
penicillium fungi
Pooja
when I finish with my bsc in microbiology where wil I work
Usman
Why can we see ourselves in a mirror?
Usman
mention 5 characteristics of prokaryotic cell and also 5 characteristics of euryotic cell
Grace Reply
PROKARYOTES _ does not have nucleus _does not have membrane bound organels like eukaryotes -does not have endoplasmic reticulum _does not have a mitchochondrion _it have plasmid instead of chromosome EUKARYOTE S _have true nucleus _have all membrane bound organels _have mitochondria have
Pooja
continuation _have endoplasmic reticulum _have chromosomes does not have plasmid
Pooja
antigenisity define
kalai
explanation of spores
nahida Reply
what specific types of biological macromolecules do living things require?
Jonathan Reply
define spores its classification
nahida
define spores its structure and classification
nahida
what is a complement
Alecia Reply
something which completes or combine with something else to make it complete.
Kosi
hello
Kosi
medical microbiology
Kosi
you?
Kosi
hi
Amina
Guys who's doing nursing in here
Mumba
I have a question
Mumba
what's the importance of microbiology in nursing
Mumba
yah
Mumba
wow..nice meeting you
Kosi
thanks
Mumba
for
Mumba
anytime
Mumba
microbiology also important for understanding the communicable or non-communicable disease in our hospitals...which is very important for patients and healthy people.
Kiran
what is a microbial flora
Chetan
normal microbial flora
Chetan
Definition of microbiology?
Mohamed Reply
study of microorganisms is known as microbiology
Pooja
no
Mumba
microbiology is the study of small or minute organisms that cannot be seen with our naked eyes but with the aid of a microscope
Mumba

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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