1. Viral Infections of the Respiratory Tract and Skin
Chapter 15
Viral Infections of the Respiratory Tract and Skin

2. 15.1 Viruses Account for Most Upper Respiratory Tract Infections
Rhinovirus infections are the chief cause of the common cold.
Thrive in the lower temperature of the nose (33oC)
They are transmitted by airborne respiratory droplets or contact with contaminated objects.
Figure 15.02: A Rhinovirus.
Human rhinovirus 16: Picornaviridae; Rhinovirus; Human rhinovirus A; strain (NA).
Hadfield, A.T., Lee, W.M., Zhao, R., Oliveira, M.A., Minor, I., Rueckert, R.R. and Rossmann, M.G. (1997). The refined structure of human rhinovirus 16 at 2.15 A resolution:

3. Figure 15.03: Seasonal Variation of Viral Respiratory Diseases.
Rhinoviruses are responsible for 30-50% of the cases of the common cold.
More than 200 different virus strains can cause common colds.
Researchers are studying the genome sequences for more than 100 rhinoviruses.
They have found common genes to possibly develop a vaccine.
Figure 15.03: Seasonal Variation of Viral Respiratory Diseases.

4. Adenovirus infections also produce symptoms typical of a common cold.
Some Adenoviruses are frequent causes of acute upper respiratory infections
Infection can cause:
acute febrile pharyngitis.
pharyngoconjuntival fever.
acute respiratory disease (ARD) in military recruits (vaccine available)
May progress to viral pneumonia.
Figure 15.04: An Adenovirus.
© Dr. Linda Stannard, UCT/Photo Researchers, Inc.

5. 15.2 Viral Infections of the Lower Respiratory Tract Can Be Severe
Influenza is a highly communicable acute respiratory infection.
It is transmitted by airborne respiratory droplets.
There have been at least 31 influenza pandemics since 1510.

6. Figure 15.05: Influenza A virus.
Influenza contains two types of spikes.
Hemagglutin (H) helps the virion attach and penetrate host cells.
Neuraminidase (N) helps release virions from the host cell after replication and assembly.
Each year a slightly different seasonal flu strain evolves
Figure 15.05: Influenza A virus.

7. Figure MF15.03: Preschoolers drive flu outbreaks.
Influenza A strikes every year and causes most epidemics.
Influenza B also strikes every year but is less common than type A.
Influenza C causes a mild respiratory illness but not epidemics.
Complications:
Guillain-Barre syndrome damages nerves
Reye syndrome from kids using aspirin
Figure MF15.03: Preschoolers drive flu outbreaks.
© Cristina Fumi/ShutterStock, Inc.

8. Figure MI 15: How Influenza Viruses Evolve.
A new flu strain evolves every year, requiring development of a new vaccine – a mixture of the most common type A and B subtypes.
Antigenic drift involves small changes to the virus
Antigenic shift is abrupt, major changes to Influenza A virus, causing epidemics
Figure MI 15: How Influenza Viruses Evolve.

9. Figure 15.06: The Relationships between the Human Paramyxoviruses.
Paramyxovirus infections affect the lower respiratory tract.
Figure 15.06: The Relationships between the Human Paramyxoviruses.

10. Figure 15.07: The Parainfluenza Virus.
Respiratory syncytial (RS) disease is caused by the respiratory syncytial virus (RSV).
It commonly affects children under 1 year of age.
It infects the bronchioles and alveoli of the lungs, causing cells to fuse together into syncytia.
Parainfluenza infections are usually
caused by human parainfluenza
viruses 1 and 3.
Infections are milder than influenza.
Human metapneumovirus (hMPV) are RSV-like viruses.
Symptoms are milder than RS disease.
Figure 15.07: The Parainfluenza Virus.
© Gopal Murti/Phototake/Alamy Images

11. Textbook case 15 2002-2003 Outbreak of SARS.
Severe acute respiratory syndrome (SARS) spreads through close person-to-person contact.
SARS is an emerging infectious disease
It is spread by contact with an infected person or an object upon which they have coughed or sneezed.
All SARS patients should be isolated for at least 10 days after fever has broken to prevent spread.
Textbook case Outbreak of SARS.

12. Hantavirus Pulmonary Syndrome
Reservoir is a deer mouse, virus shed in saliva, urine and feces.
1-5 weeks after exposure symptoms of fatigue, fever and muscle aches begin.
Can lead to respiratory failure as lungs fill with fluid
Found in the desert SW in wet years
Prevented by eliminating rodent nests
Figure 15.08: The Hantavirus.
© Chris Bjornberg/Photo Researchers, Inc.

13. 15.3 Herpesviruses Cause Several Human Skin Diseases
Human herpes simplex infections are widespread and often recurrent.
Figure 15.09: The Relationships between the Human Herpesviruses.

14. Cold sores are contagious sores caused by HSV-1.
After primary infection, the viruses become latent in sensory ganglia.
Recurrence of cold sores occurs when viruses are reactivated and move to the epithelium.
Figure 15.10A: Herpes Simplex Virus.
© Phototake/Alamy Images
Figure 15.10B: Herpes sore on mouth.
Courtesy of Dr. Hermann/CDC

15. Figure 15.12: Genital Herpes Rash on the Penile Shaft.
Genital herpes is a common STD, caused usually by HSV-2.
Symptoms include:
itching and throbbing in the genital area.
followed by blisters.
There is no cure, but antivirals can shorten and decrease the number of outbreaks.
Figure 15.12: Genital Herpes Rash on the Penile Shaft.
Courtesy of Dr. N.J. Flumara and Dr. Gavin Hart/CDC

16. Infection of the eye is called herpes keratitis.
It can cause scarring of the cornea and blindness.
Neonatal herpes is a life-threatening disease passed from infected mothers to newborns during childbirth.
The child’s mental development can be delayed.
Blindness and seizures can occur.

17. Figure 15.13A: Child with chicken pox.
Chickenpox is no longer a prevalent disease in the United States.
A vaccine using attenuated viruses became available in 1995.
It is a highly communicable disease caused by the varicella-zoster virus (VZV).
It is transmitted by skin contact and respiratory droplets.
A red, itchy rash spreads across the entire body and turns into fluid-filled vesicles which break open and yield highly infectious virus-laden fluid.
The most common complication is bacterial infection of the skin.
Figure 15.13A: Child with chicken pox.
© SW Productions/age fotostock

18. Figure 15.13B: Shingles lesions.
Shingles is an adult disease caused by the same virus as chickenpox.
After infection, VZV can remain in nerve cells for many years.
If they are reactivated, they can travel to the body trunk and cause blisters and patches of red.
It can also cause facial paralysis and severe “ice-pick” pains.
It can occur repeatedly.
Postherpetic neuralgia is the persistence of shingles pain for years after the blisters have disappeared.
Zostavax is a vaccination to prevent Shingles.
Figure 15.13B: Shingles lesions.
© Science Photo Library/Photo Researchers, Inc.

19. Human herpesvirus 6 infections primarily occur in infancy.
It causes roseola in infants, marked by:
high fever.
subsequent red rash.
It is spread through contact with respiratory secretions or saliva.
Many bone barrow transplant recipients suffer an HHV-6 viremia after transplantation.
May potentially lead to pneumonia or encephalitis.
Figure 15.14: Roseola.
© Scott Camazine & Sue Trainor/Photo Researchers, Inc.

20. Figure 15.15: Kaposi's Sarcoma.
Kaposi sarcoma is an angiogenic tumor of the blood vessel walls.
It is most commonly seen in immunocompromised individuals, such as AIDS patients.
It is caused by HHV-8, forming dark or purple skin lesions.
Figure 15.15: Kaposi's Sarcoma.
Courtesy of National Cancer Institute

21. 15.4 Several Other Viral Diseases of Affect the Skin
© Medical-on-Line/Alamy Images
Paramyxovirus infections can cause typical childhood diseases.
Measles (rubeola) is a highly contagious disease
Transmission occurs through respiratory droplets.
Koplik spots are red patches with white grain-like centers that appear along the gum line.
The characteristic red rash
Vaccine is given in the MMR inoculation.
Complications can be subacute sclerosing panencepalitis or Paget’s disease of the bone
Figure 15.16A: Koplik Spots.
Courtesy of CDC
Figure 15.16B: Measles.

22. Mumps (infectious parotitis) is characterized by enlarged jaw tissues caused by swollen salivary glands.
The swelling is caused by blockage of ducts leading from the parotid glands.
It is spread by respiratory droplets or contact with contaminated objects.
In males, swelling and damage may occur in the testes (orchitis).
Prevented by MMR vaccine
Figure 15.17: Mumps.
Courtesy of NIP/Barbara Rice/CDC

23. Rubella (German Measles) is an acute, mildly infectious disease.
It is transmitted by respiratory droplets or contact.
Symptoms of rubella include an occasional fever and pale-pink maculopapular rash.
Recovery is usually prompt, but relapses can occur.
Congenital rubella occurs when the fetus is infected through the placenta.
Children may be born with problems in the: eye, ear, heart
Prevented by the MMR vaccine.

24. Fifth disease (Erythema Infectiosum) produces a mild rash
It is caused by human parvovirus B19
Transmission occurs through respiratory droplets.
Symptoms include a fiery red rash on the cheeks and ears, and trunk.
It disappears within a few days.
Adults can experience symptoms similar to those of rheumatoid arthritis.
Figure 15.18: Fifth Disease.
© Dr. Ken Greer/Visuals Unlimited

25. Figure 15.20: Early stages of cervical cancer.
Some Human Papillomavirus infections cause warts.
Common warts are usually benign skin growths resulting from a strain of HPV.
Plantar warts are on the soles of the feet.
They can be transmitted by contact with:
an affected person.
a contaminated object.
Genital warts (condylomata) are often transmitted through sexual contact.
Some strains of HPV are associated with cervical cancer.
They may be transmitted to newborns during delivery.
There is a new vaccine Gardasil for some strains.
© Medical-on-Line/Alamy Images
Figure MF 15.5: Skin warts.
Courtesy of CDC
Figure 15.20: Early stages of cervical cancer.

26. Figure 15.22A: The Lesions of Smallpox.
Poxvirus infections have had great medical impacts on populations.
Smallpox (variola) is contagious, and sometimes fatal.
Pink-red macules appear on the face and trunk.
They then become papules, and fluid-filled vesicles.
The vesicles become pustules that break open and emit puss, leaving pitted scars (pocks).
Figure 15.22A: The Lesions of Smallpox.
Courtesy of World Health Organization; Diagnosis of Smallpox Slide Series/CDC

27. Figure 15.21A: The Smallpox Virus.
Vaccinations ceased in the U.S. in 1972 after eradication occurred, so many people are not immune.
Smallpox is one of the most dangerous weapons of bioterrorism.
Figure 15.21A: The Smallpox Virus.