Running head: PATHOGENICITY AND VIRULENCE

Pathogenicity and Virulence

June Saxton

Kaplan University

HS320

Susan Galindo

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PATHOGENICITY AND VIRULENCE

Pathogenicity and Virulence

Introduction

Microbes are all around us both outside of our bodies and inside our bodies and a lot of

the time we maintain a delicate balance with them and coexist with them to the mutual benefit of

both of us but when our relationship tilts in the favor of the microbe infection and disease occur

(Pommerville, 2011).

Pathogenicity and virulence

When a microorganism gains entry into our bodies and alters our tissues changing them

physiologically or anatomically our health is compromised and disease occurs. Virulence refers

to the degree and severity of the disease that the microorganism causes and the amount of harm

that it is capable of causing to our bodies (Pommerville, 2011).

The pathogens which cause cholera, plague and typhoid are well known for their ability

to cause disease and are highly virulent. Other pathogens such as the cold virus and Candida

albicans are mildly virulent because they either cause a milder illness or only cause disease

sometimes. There are also microorganisms which that do not cause disease to us such as the

lactobacilli and streptococci found in yogurt. These are called avirulent (Pommerville).

When the relationship between us and the microorganism is to the benefit of both us it is

called mutualism and when the relationship is beneficial to the microorganism and the host is

unaffected it is called commensalism. There are times, however, when commensal organisms

take advantage of a weakened immune system and invade and cause disease (Pommerville,

2011). For example, when AIDS/HIV weakens the immune system the normally mild Candida

fungus can cause Thrush which is a serious infection of the tongue and the throat. Pneumonia is

often fatal when someone has AIDS because their weakened immune systems are unable to fight

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PATHOGENICITY AND VIRULENCE

the pathogen.

Public Health Implications

Infectious diseases continue to be a public health problem because of the unique ability of

microorganisms to change over time. In addition to the persistent infections that still exist, new

and reemerging diseases cause new public health concerns (Johns Hopkins University School of

Public Health, 2005). The World Health Organization reported in 1998 that 25% of deaths

worldwide were caused by infectious diseases (World Health Organization, 1999).

Public Health organizations including the CDC and World Health Organization have

plans in place to limit and stop infectious diseases. For example, the CDC’s Infectious Disease

Framework provides a roadmap for community public health and healthcare communities to

protect people and individuals from infectious diseases and to prevent and respond to outbreaks.

Their role is to provide leadership and the technical expertise necessary (CDC, 2011).

The CDC’s priorities with regard to infectious disease are: to assist in maintaining control

of new pathogens, global disease surveillance and provide early warning of emerging health

threats, research on diseases to affect the global population, establishing global disease control

initiatives to reduce HIV/AIDS, malaria and TB and to provide public health training to

developing nations (Pommerville, 2011).

It is important to understand how microbes become pathogens, how they become virulent

and how they take advantage of weakened immune systems in order for us to do our part to

prevent infectious diseases.

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PATHOGENICITY AND VIRULENCE

References

CDC. (2011, October). A cdc framework for preventing infectious diseases. Retrieved from

http://www.cdc.gov/oid/docs/ID-Framework-2pageoverview.pdf

Johns Hopkins University School of Public Health. (2005, March 25). Infectious diseases still

major public health threat, fauci says. Retrieved from

http://www.jhsph.edu/news/stories/2005/fauci.html

Pommerville, J. (2011). Alcamo's fundamentals of microbiology. (9 ed., Vol. 9). Sudbury: Jones

& Bartlett Publishers.

WebMD, LLC. (2013). Hiv/aids and opportunistic infections. Retrieved from

http://www.webmd.com/hiv-aids/guide/aids-hiv-opportunistic-infections-html

World Health Organization. (1999, March 25). Leading causes of death. Retrieved from

http://www.who.int/infectious-disease-report/pages/graph1.html

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