Plate 85

Viral Diseases of the Respiratory System

Respiratory System

• The respiratory system is responsible for oxygenating the blood and removing waste carbon dioxide from the blood

Respiratory System

• Alveoli are the final branches of the “respiratory tree”

• Allow gases to exchange between the lungs and the blood

• Tissue between alveoli and capillaries is very thin – allowing for easy gas exchange

Viral Diseases of the Respiratory System

• Most viral diseases do not directly kill the host organism

• Rather, the viruses destroy cells within the respiratory system, making them susceptible to bacterial infection– Staphylococci– Streptococci

Influenza• Human influenza viruses (helical, RNA viruses)• Type A

– Causes seasonal epidemics– Found in ducks, chickens, pigs, whales, horses, and seals– Categorized into subtypes based upon surface proteins

• Hemagglutinin (H)– 16 variations

• Neuraminidase (N)– 9 variations

• Current strains include H1N1 and H3N2

• Type B– Causes seasonal epidemics– Only found in humans

• Type C– Causes mild respiratory illness

Novel H1N1 – “Swine Flu”

• Caused by “antigenic shift” – a major change in the virus with a new combination of hemagglutinin and neuraminidase proteins

• So different from other influenza viruses that most people don’t have immunity to it

• Pigs can be infected with human and avian influenza viruses, and they can mix

• It’s thought that “Swine Flu” has genes mostly from a human virus, but surface proteins from an avian virus

Influenza Symptoms

• Fever• Cough• Sore throat• Runny or stuffy nose• Muscle or body aches• Headaches• Fatigue

Peak Months of Influenza Activity

Influenza Complications

• Bacterial pneumonia• Ear infections• Sinus infections

Influenza Vaccinations

• CDC recommends “universal” flu vaccinations• Especially the following groups:– Pregnant women– Children younger than 5– People 50+ years old

Influenza Transmission

• Spread through respiratory droplets• Also possible to get by touching a surface that

has the virus on it, then touching your eyes, mouth, or nose

• May be able to infect others 1 day before symptoms appear and 5-7 days after becoming sick

• http://www.flu.gov/video/psa/stay_healthy_america.html

Severe Acute Respiratory Syndrome (SARS)

Severe Acute Respiratory Syndrome (SARS)

• Caused by a coronavirus (SARS-associated coronavirus)

• Coronaviruses have been linked pneumonia• The virus may survive in the environment for

several days

SARS Symptoms

• High fever (>100.4° F)• Headache• Discomfort• Body aches• Diarrhea• Pneumonia

SARS Transmission

• Spread through respiratory droplets• Spread through touching a contaminated object,

then touching your mouth, nose, or eyes• “Close contact” – living with someone with SARS,

having direct contact with body fluids from a patient

• Incubation period is between 2-7 days, but the disease is only contagious while symptoms are present

Global SARS Outbreak (2003)

• Between November 2002 – July 2003– 8,098 people became infected worldwide– 774 died– 8 people in U.S. were confirmed to have SARS, 0

deaths

Common Cold

• More than 200 viruses cause the “common cold”

• Rhinoviruses and adenoviruses are the most common

Common Cold - Symptoms

• Sneezing• Stuffy or runny nose• Sore throat• Coughing• Mild headache• Mild body aches

Common Cold – Runny Nose

• Nose makes clean mucus when infected to wash the virus from the sinuses

• Immune cells begin to fight the virus, changing the mucus to a white or yellow color

• As bacteria in nose grow back, they may change the mucus to a greenish color