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Microbiology

21.3 Viral Infections of the Skin and Eyes

Microbiology 21.3 Viral Infections of the Skin and Eyes
  1. Preface
  2. 1 An Invisible World
    1. Introduction
    2. 1.1 What Our Ancestors Knew
    3. 1.2 A Systematic Approach
    4. 1.3 Types of Microorganisms
    5. Summary
    6. Review Questions
      1. Multiple Choice
      2. Fill in the Blank
      3. Short Answer
      4. Critical Thinking
  3. 2 How We See the Invisible World
    1. Introduction
    2. 2.1 The Properties of Light
    3. 2.2 Peering Into the Invisible World
    4. 2.3 Instruments of Microscopy
    5. 2.4 Staining Microscopic Specimens
    6. Summary
    7. Review Questions
      1. Multiple Choice
      2. Fill in the Blank
      3. Short Answer
      4. Critical Thinking
  4. 3 The Cell
    1. Introduction
    2. 3.1 Spontaneous Generation
    3. 3.2 Foundations of Modern Cell Theory
    4. 3.3 Unique Characteristics of Prokaryotic Cells
    5. 3.4 Unique Characteristics of Eukaryotic Cells
    6. Summary
    7. Review Questions
      1. Multiple Choice
      2. True/False
      3. Fill in the Blank
      4. Short Answer
      5. Critical Thinking
  5. 4 Prokaryotic Diversity
    1. Introduction
    2. 4.1 Prokaryote Habitats, Relationships, and Microbiomes
    3. 4.2 Proteobacteria
    4. 4.3 Nonproteobacteria Gram-Negative Bacteria and Phototrophic Bacteria
    5. 4.4 Gram-Positive Bacteria
    6. 4.5 Deeply Branching Bacteria
    7. 4.6 Archaea
    8. Summary
    9. Review Questions
      1. Multiple Choice
      2. True/False
      3. Fill in the Blank
      4. Short Answer
      5. Critical Thinking
  6. 5 The Eukaryotes of Microbiology
    1. Introduction
    2. 5.1 Unicellular Eukaryotic Parasites
    3. 5.2 Parasitic Helminths
    4. 5.3 Fungi
    5. 5.4 Algae
    6. 5.5 Lichens
    7. Summary
    8. Review Questions
      1. Multiple Choice
      2. Fill in the Blank
      3. Short Answer
      4. Critical Thinking
  7. 6 Acellular Pathogens
    1. Introduction
    2. 6.1 Viruses
    3. 6.2 The Viral Life Cycle
    4. 6.3 Isolation, Culture, and Identification of Viruses
    5. 6.4 Viroids, Virusoids, and Prions
    6. Summary
    7. Review Questions
      1. Multiple Choice
      2. True/False
      3. Fill in the Blank
      4. Short Answer
      5. Critical Thinking
  8. 7 Microbial Biochemistry
    1. Introduction
    2. 7.1 Organic Molecules
    3. 7.2 Carbohydrates
    4. 7.3 Lipids
    5. 7.4 Proteins
    6. 7.5 Using Biochemistry to Identify Microorganisms
    7. Summary
    8. Review Questions
      1. Multiple Choice
      2. True/False
      3. Matching
      4. Fill in the Blank
      5. Short Answer
      6. Critical Thinking
  9. 8 Microbial Metabolism
    1. Introduction
    2. 8.1 Energy, Matter, and Enzymes
    3. 8.2 Catabolism of Carbohydrates
    4. 8.3 Cellular Respiration
    5. 8.4 Fermentation
    6. 8.5 Catabolism of Lipids and Proteins
    7. 8.6 Photosynthesis
    8. 8.7 Biogeochemical Cycles
    9. Summary
    10. Review Questions
      1. Multiple Choice
      2. True/False
      3. Matching
      4. Fill in the Blank
      5. Short Answer
      6. Critical Thinking
  10. 9 Microbial Growth
    1. Introduction
    2. 9.1 How Microbes Grow
    3. 9.2 Oxygen Requirements for Microbial Growth
    4. 9.3 The Effects of pH on Microbial Growth
    5. 9.4 Temperature and Microbial Growth
    6. 9.5 Other Environmental Conditions that Affect Growth
    7. 9.6 Media Used for Bacterial Growth
    8. Summary
    9. Review Questions
      1. Multiple Choice
      2. Matching
      3. Fill in the Blank
      4. Short Answer
      5. Critical Thinking
  11. 10 Biochemistry of the Genome
    1. Introduction
    2. 10.1 Using Microbiology to Discover the Secrets of Life
    3. 10.2 Structure and Function of DNA
    4. 10.3 Structure and Function of RNA
    5. 10.4 Structure and Function of Cellular Genomes
    6. Summary
    7. Review Questions
      1. Multiple Choice
      2. True/False
      3. Matching
      4. Fill in the Blank
      5. Short Answer
      6. Critical Thinking
  12. 11 Mechanisms of Microbial Genetics
    1. Introduction
    2. 11.1 The Functions of Genetic Material
    3. 11.2 DNA Replication
    4. 11.3 RNA Transcription
    5. 11.4 Protein Synthesis (Translation)
    6. 11.5 Mutations
    7. 11.6 How Asexual Prokaryotes Achieve Genetic Diversity
    8. 11.7 Gene Regulation: Operon Theory
    9. Summary
    10. Review Questions
      1. Multiple Choice
      2. True/False
      3. Fill in the Blank
      4. Short Answer
      5. Critical Thinking
  13. 12 Modern Applications of Microbial Genetics
    1. Introduction
    2. 12.1 Microbes and the Tools of Genetic Engineering
    3. 12.2 Visualizing and Characterizing DNA, RNA, and Protein
    4. 12.3 Whole Genome Methods and Pharmaceutical Applications of Genetic Engineering
    5. 12.4 Gene Therapy
    6. Summary
    7. Review Questions
      1. Multiple Choice
      2. True/False
      3. Fill in the Blank
      4. Short Answer
      5. Critical Thinking
  14. 13 Control of Microbial Growth
    1. Introduction
    2. 13.1 Controlling Microbial Growth
    3. 13.2 Using Physical Methods to Control Microorganisms
    4. 13.3 Using Chemicals to Control Microorganisms
    5. 13.4 Testing the Effectiveness of Antiseptics and Disinfectants
    6. Summary
    7. Review Questions
      1. Multiple Choice
      2. True/False
      3. Fill in the Blank
      4. Short Answer
      5. Critical Thinking
  15. 14 Antimicrobial Drugs
    1. Introduction
    2. 14.1 History of Chemotherapy and Antimicrobial Discovery
    3. 14.2 Fundamentals of Antimicrobial Chemotherapy
    4. 14.3 Mechanisms of Antibacterial Drugs
    5. 14.4 Mechanisms of Other Antimicrobial Drugs
    6. 14.5 Drug Resistance
    7. 14.6 Testing the Effectiveness of Antimicrobials
    8. 14.7 Current Strategies for Antimicrobial Discovery
    9. Summary
    10. Review Questions
      1. Multiple Choice
      2. True/False
      3. Fill in the Blank
      4. Short Answer
      5. Critical Thinking
  16. 15 Microbial Mechanisms of Pathogenicity
    1. Introduction
    2. 15.1 Characteristics of Infectious Disease
    3. 15.2 How Pathogens Cause Disease
    4. 15.3 Virulence Factors of Bacterial and Viral Pathogens
    5. 15.4 Virulence Factors of Eukaryotic Pathogens
    6. Summary
    7. Review Questions
      1. Multiple Choice
      2. Fill in the Blank
      3. Short Answer
      4. Critical Thinking
  17. 16 Disease and Epidemiology
    1. Introduction
    2. 16.1 The Language of Epidemiologists
    3. 16.2 Tracking Infectious Diseases
    4. 16.3 Modes of Disease Transmission
    5. 16.4 Global Public Health
    6. Summary
    7. Review Questions
      1. Multiple Choice
      2. Matching
      3. Fill in the Blank
      4. Short Answer
      5. Critical Thinking
  18. 17 Innate Nonspecific Host Defenses
    1. Introduction
    2. 17.1 Physical Defenses
    3. 17.2 Chemical Defenses
    4. 17.3 Cellular Defenses
    5. 17.4 Pathogen Recognition and Phagocytosis
    6. 17.5 Inflammation and Fever
    7. Summary
    8. Review Questions
      1. Multiple Choice
      2. Matching
      3. Fill in the Blank
      4. Short Answer
      5. Critical Thinking
  19. 18 Adaptive Specific Host Defenses
    1. Introduction
    2. 18.1 Overview of Specific Adaptive Immunity
    3. 18.2 Major Histocompatibility Complexes and Antigen-Presenting Cells
    4. 18.3 T Lymphocytes and Cellular Immunity
    5. 18.4 B Lymphocytes and Humoral Immunity
    6. 18.5 Vaccines
    7. Summary
    8. Review Questions
      1. Multiple Choice
      2. Matching
      3. Fill in the Blank
      4. Short Answer
      5. Critical Thinking
  20. 19 Diseases of the Immune System
    1. Introduction
    2. 19.1 Hypersensitivities
    3. 19.2 Autoimmune Disorders
    4. 19.3 Organ Transplantation and Rejection
    5. 19.4 Immunodeficiency
    6. 19.5 Cancer Immunobiology and Immunotherapy
    7. Summary
    8. Review Questions
      1. Multiple Choice
      2. Matching
      3. Fill in the Blank
      4. Short Answer
      5. Critical Thinking
  21. 20 Laboratory Analysis of the Immune Response
    1. Introduction
    2. 20.1 Polyclonal and Monoclonal Antibody Production
    3. 20.2 Detecting Antigen-Antibody Complexes
    4. 20.3 Agglutination Assays
    5. 20.4 EIAs and ELISAs
    6. 20.5 Fluorescent Antibody Techniques
    7. Summary
    8. Review Questions
      1. Multiple Choice
      2. Fill in the Blank
      3. Short Answer
      4. Critical Thinking
  22. 21 Skin and Eye Infections
    1. Introduction
    2. 21.1 Anatomy and Normal Microbiota of the Skin and Eyes
    3. 21.2 Bacterial Infections of the Skin and Eyes
    4. 21.3 Viral Infections of the Skin and Eyes
    5. 21.4 Mycoses of the Skin
    6. 21.5 Protozoan and Helminthic Infections of the Skin and Eyes
    7. Summary
    8. Review Questions
      1. Multiple Choice
      2. Fill in the Blank
      3. Short Answer
      4. Critical Thinking
  23. 22 Respiratory System Infections
    1. Introduction
    2. 22.1 Anatomy and Normal Microbiota of the Respiratory Tract
    3. 22.2 Bacterial Infections of the Respiratory Tract
    4. 22.3 Viral Infections of the Respiratory Tract
    5. 22.4 Respiratory Mycoses
    6. Summary
    7. Review Questions
      1. Multiple Choice
      2. Fill in the Blank
      3. Short Answer
      4. Critical Thinking
  24. 23 Urogenital System Infections
    1. Introduction
    2. 23.1 Anatomy and Normal Microbiota of the Urogenital Tract
    3. 23.2 Bacterial Infections of the Urinary System
    4. 23.3 Bacterial Infections of the Reproductive System
    5. 23.4 Viral Infections of the Reproductive System
    6. 23.5 Fungal Infections of the Reproductive System
    7. 23.6 Protozoan Infections of the Urogenital System
    8. Summary
    9. Review Questions
      1. Multiple Choice
      2. Fill in the Blank
      3. Short Answer
      4. Critical Thinking
  25. 24 Digestive System Infections
    1. Introduction
    2. 24.1 Anatomy and Normal Microbiota of the Digestive System
    3. 24.2 Microbial Diseases of the Mouth and Oral Cavity
    4. 24.3 Bacterial Infections of the Gastrointestinal Tract
    5. 24.4 Viral Infections of the Gastrointestinal Tract
    6. 24.5 Protozoan Infections of the Gastrointestinal Tract
    7. 24.6 Helminthic Infections of the Gastrointestinal Tract
    8. Summary
    9. Review Questions
      1. Multiple Choice
      2. Fill in the Blank
      3. Short Answer
      4. Critical Thinking
  26. 25 Circulatory and Lymphatic System Infections
    1. Introduction
    2. 25.1 Anatomy of the Circulatory and Lymphatic Systems
    3. 25.2 Bacterial Infections of the Circulatory and Lymphatic Systems
    4. 25.3 Viral Infections of the Circulatory and Lymphatic Systems
    5. 25.4 Parasitic Infections of the Circulatory and Lymphatic Systems
    6. Summary
    7. Review Questions
      1. Multiple Choice
      2. Fill in the Blank
      3. Short Answer
      4. Critical Thinking
  27. 26 Nervous System Infections
    1. Introduction
    2. 26.1 Anatomy of the Nervous System
    3. 26.2 Bacterial Diseases of the Nervous System
    4. 26.3 Acellular Diseases of the Nervous System
    5. 26.4 Fungal and Parasitic Diseases of the Nervous System
    6. Summary
    7. Review Questions
      1. Multiple Choice
      2. Matching
      3. Fill in the Blank
      4. Short Answer
      5. Critical Thinking
  28. A | Fundamentals of Physics and Chemistry Important to Microbiology
  29. B | Mathematical Basics
  30. C | Metabolic Pathways
  31. D | Taxonomy of Clinically Relevant Microorganisms
  32. E | Glossary
  33. Answer Key
    1. Chapter 1
    2. Chapter 2
    3. Chapter 3
    4. Chapter 4
    5. Chapter 5
    6. Chapter 6
    7. Chapter 7
    8. Chapter 8
    9. Chapter 9
    10. Chapter 10
    11. Chapter 11
    12. Chapter 12
    13. Chapter 13
    14. Chapter 14
    15. Chapter 15
    16. Chapter 16
    17. Chapter 17
    18. Chapter 18
    19. Chapter 19
    20. Chapter 20
    21. Chapter 21
    22. Chapter 22
    23. Chapter 23
    24. Chapter 24
    25. Chapter 25
    26. Chapter 26
  34. Index

Learning Objectives

  • Identify the most common viruses associated with infections of the skin and eyes
  • Compare the major characteristics of specific viral diseases affecting the skin and eyes

Until recently, it was thought that the normal microbiota of the body consisted primarily of bacteria and some fungi. However, in addition to bacteria, the skin is colonized by viruses, and recent studies suggest that Papillomaviridae, Polyomaviridae and Circoviridae also contribute to the normal skin microbiota. However, some viruses associated with skin are pathogenic, and these viruses can cause diseases with a wide variety of presentations.

Numerous types of viral infections cause rashes or lesions on the skin; however, in many cases these skin conditions result from infections that originate in other body systems. In this chapter, we will limit the discussion to viral skin infections that use the skin as a portal of entry. Later chapters will discuss viral infections such as chickenpox, measles, and rubella—diseases that cause skin rashes but invade the body through portals of entry other than the skin.

Papillomas

Papillomas (warts) are the expression of common skin infections by human papillomavirus (HPV) and are transmitted by direct contact. There are many types of HPV, and they lead to a variety of different presentations, such as common warts, plantar warts, flat warts, and filiform warts. HPV can also cause sexually-transmitted genital warts, which will be discussed in Urogenital System Infections. Vaccination is available for some strains of HPV.

Common warts tend to develop on fingers, the backs of hands, and around nails in areas with broken skin. In contrast, plantar warts (also called foot warts) develop on the sole of the foot and can grow inwards, causing pain and pressure during walking. Flat warts can develop anywhere on the body, are often numerous, and are relatively smooth and small compared with other wart types. Filiform warts are long, threadlike warts that grow quickly.

In some cases, the immune system may be strong enough to prevent warts from forming or to eradicate established warts. However, treatment of established warts is typically required. There are many available treatments for warts, and their effectiveness varies. Common warts can be frozen off with liquid nitrogen. Topical applications of salicylic acid may also be effective. Other options are electrosurgery (burning), curettage (cutting), excision, painting with cantharidin (which causes the wart to die so it can more easily be removed), laser treatments, treatment with bleomycin, chemical peels, and immunotherapy (Figure 21.25).

a) photo of warts on a toe. B) photo of wart on an eye.
Figure 21.25 Warts can vary in shape and in location. (a) Multiple plantar warts have grown on this toe. (b) A filiform wart has grown on this eyelid.

Oral Herpes

Another common skin virus is herpes simplex virus (HSV). HSV has historically been divided into two types, HSV-1 and HSV-2. HSV-1 is typically transmitted by direct oral contact between individuals, and is usually associated with oral herpes. HSV-2 is usually transmitted sexually and is typically associated with genital herpes. However, both HSV-1 and HSV-2 are capable of infecting any mucous membrane, and the incidence of genital HSV-1 and oral HSV-2 infections has been increasing in recent years. In this chapter, we will limit our discussion to infections caused by HSV-1; HSV-2 and genital herpes will be discussed in Urogenital System Infections.

Infection by HSV-1 commonly manifests as cold sores or fever blisters, usually on or around the lips (Figure 21.26). HSV-1 is highly contagious, with some studies suggesting that up to 65% of the US population is infected; however, many infected individuals are asymptomatic.15 Moreover, the virus can be latent for long periods, residing in the trigeminal nerve ganglia between recurring bouts of symptoms. Recurrence can be triggered by stress or environmental conditions (systemic or affecting the skin). When lesions are present, they may blister, break open, and crust. The virus can be spread through direct contact, even when a patient is asymptomatic.

While the lips, mouth, and face are the most common sites for HSV-1 infections, lesions can spread to other areas of the body. Wrestlers and other athletes involved in contact sports may develop lesions on the neck, shoulders, and trunk. This condition is often called herpes gladiatorum. Herpes lesions that develop on the fingers are often called herpetic whitlow.

HSV-1 infections are commonly diagnosed from their appearance, although laboratory testing can confirm the diagnosis. There is no cure, but antiviral medications such as acyclovir, penciclovir, famciclovir, and valacyclovir are used to reduce symptoms and risk of transmission. Topical medications, such as creams with n-docosanol and penciclovir, can also be used to reduce symptoms such as itching, burning, and tingling.

Photo of cold sore on a lip.
Figure 21.26 This cold sore was caused by HSV-1. (credit: Centers for Disease Control and Prevention)

Check Your Understanding

  • What are the most common sites for the appearance of herpetic lesions?

Roseola and Fifth Disease

The viral diseases roseola and fifth disease are somewhat similar in terms of their presentation, but they are caused by different viruses. Roseola, sometimes called roseola infantum or exanthem subitum (“sudden rash”), is a mild viral infection usually caused by human herpesvirus-6 (HHV-6) and occasionally by HHV-7. It is spread via direct contact with the saliva or respiratory secretions of an infected individual, often through droplet aerosols. Roseola is very common in children, with symptoms including a runny nose, a sore throat, and a cough, along with (or followed by) a high fever (39.4 ºC). About three to five days after the fever subsides, a rash may begin to appear on the chest and abdomen. The rash, which does not cause discomfort, initially forms characteristic macules that are flat or papules that are firm and slightly raised; some macules or papules may be surrounded by a white ring. The rash may eventually spread to the neck and arms, and sometimes continues to spread to the face and legs. The diagnosis is generally made based upon observation of the symptoms. However, it is possible to perform serological tests to confirm the diagnosis. While treatment may be recommended to control the fever, the disease usually resolves without treatment within a week after the fever develops. For individuals at particular risk, such as those who are immunocompromised, the antiviral medication ganciclovir may be used.

Fifth disease (also known as erythema infectiosum) is another common, highly contagious illness that causes a distinct rash that is critical to diagnosis. Fifth disease is caused by parvovirus B19, and is transmitted by contact with respiratory secretions from an infected individual. Infection is more common in children than adults. While approximately 20% of individuals will be asymptomatic during infection,16 others will exhibit cold-like symptoms (headache, fever, and upset stomach) during the early stages when the illness is most infectious. Several days later, a distinct red facial rash appears, often called “slapped cheek” rash (Figure 21.27). Within a few days, a second rash may appear on the arms, legs, chest, back, or buttocks. The rash may come and go for several weeks, but usually disappears within seven to twenty-one days, gradually becoming lacy in appearance as it recedes.

In children, the disease usually resolves on its own without medical treatment beyond symptom relief as needed. Adults may experience different and possibly more serious symptoms. Many adults with fifth disease do not develop any rash, but may experience joint pain and swelling that lasts several weeks or months. Immunocompromised individuals can develop severe anemia and may need blood transfusions or immune globulin injections. While the rash is the most important component of diagnosis (especially in children), the symptoms of fifth disease are not always consistent. Serological testing can be conducted for confirmation.

a) photo of red patches on an infant’s legs. B) photo of red spots on a child’s trunk.
Figure 21.27 (a) Roseola, a mild viral infection common in young children, generally begins with symptoms similar to a cold, followed by a pink, patchy rash that starts on the trunk and spreads outward. (b) Fifth disease exhibits similar symptoms in children, except for the distinctive “slapped cheek” rash that originates on the face.

Check Your Understanding

  • Identify at least one similarity and one difference between roseola and fifth disease.

Viral Conjunctivitis

Like bacterial conjunctivitis viral infections of the eye can cause inflammation of the conjunctiva and discharge from the eye. However, viral conjunctivitis tends to produce a discharge that is more watery than the thick discharge associated with bacterial conjunctivitis. The infection is contagious and can easily spread from one eye to the other or to other individuals through contact with eye discharge.

Viral conjunctivitis is commonly associated with colds caused by adenoviruses; however, other viruses can also cause conjunctivitis. If the causative agent is uncertain, eye discharge can be tested to aid in diagnosis. Antibiotic treatment of viral conjunctivitis is ineffective, and symptoms usually resolve without treatment within a week or two.

Herpes Keratitis

Herpes infections caused by HSV-1 can sometimes spread to the eye from other areas of the body, which may result in keratoconjunctivitis. This condition, generally called herpes keratitis or herpetic keratitis, affects the conjunctiva and cornea, causing irritation, excess tears, and sensitivity to light. Deep lesions in the cornea may eventually form, leading to blindness. Because keratitis can have numerous causes, laboratory testing is necessary to confirm the diagnosis when HSV-1 is suspected; once confirmed, antiviral medications may be prescribed.

Disease Profile

Viral Infections of the Skin and Eyes

A number of viruses can cause infections via direct contact with skin and eyes, causing signs and symptoms ranging from rashes and lesions to warts and conjunctivitis. All of these viral diseases are contagious, and while some are more common in children (fifth disease and roseola), others are prevalent in people of all ages (oral herpes, viral conjunctivitis, papillomas). In general, the best means of prevention is avoiding contact with infected individuals. Treatment may require antiviral medications; however, several of these conditions are mild and typically resolve without treatment. Figure 21.28 summarizes the characteristics of some common viral infections of the skin and eyes.

Table titled: Viral Infections of the Skin and Eyes. Columns: Disease, Pathogen, Signs and Symptoms, Transmission, Antimicrobial Drugs. Fifth disease, Parvovirus B19, May have initial cold-like symptoms; “slapped cheek” rash, Highly contagious via respiratory secretions of infected individuals, None. Herpes keratitis, Herpes simplex virus 1 (HSV-1), Inflammation of conjunctiva and cornea; irritation, excess tears, sensitivity to light; lesions in cornea leading to blindness, Direct eye contact with discharge from herpes lesions elsewhere in the body or from another infected individual, Acyclovir, ganciclovir, famiclovir, valacyclovir. Oral herpes Herpes simplex virus 1 (HSV-1), May cause initial systemic symptoms; cold sores, Highly contagious via direct contact with infected individuals, Acyclovir, penciclovir, famiclovir, valacyclovir. Papillomas, Human papillomavirus (HPV), Common warts, plantar warts, flat warts, filiform warts, and others, Contact with infected individuals, Topical salicylic acid, cantharidin. Roseola (roseola infantum, exanthem subitum), Human herpesvirus 6 (HHV-6), human herpesvirus 7 (HHV-7), Initial cold-like symptoms with high fever, followed by a macular rash three to five days later, Spread by viral and respiratory secretions of infected individuals, Typically none; ganciclovir for immunocompromised patients. Viral conjunctivitis, Adenoviruses and others, Inflammation of the conjunctiva; watery, nonpurulent discharge, Associated with common cold; contagious via contact with eye discharge, None.
Figure 21.28

Footnotes

  • 15 Wald, A., and Corey, L. “Persistence in the Population: Epidemiology, Transmission.” In: A. Arvin, G. Campadelli-Fiume, E. Mocarski et al. Human Herpesviruses: Biology, Therapy, and Immunoprophylaxis. Cambridge: Cambridge University Press, 2007. http://www.ncbi.nlm.nih.gov/books/NBK47447/. Accessed Sept 14, 2016.
  • 16 Centers for Disease Control and Prevention. “Fifth Disease.” http://www.cdc.gov/parvovirusb19/fifth-disease.html. Accessed Sept 14, 2016.
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