Upper Respiratory Infection (cont.)
Siamak N. Nabili, MD, MPH
Dr. Nabili received his undergraduate degree from the University of California, San Diego (UCSD), majoring in chemistry and biochemistry. He then completed his graduate degree at the University of California, Los Angeles (UCLA). His graduate training included a specialized fellowship in public health where his research focused on environmental health and health-care delivery and management.
William C. Shiel Jr., MD, FACP, FACR
Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.
In this Article
- Upper respiratory infection facts
- What is an upper respiratory infection?
- Is an upper respiratory infection contagious?
- What are the causes of upper respiratory infection?
- What are the risk factors for upper respiratory infection?
- What are the symptoms of upper respiratory infection?
- When should you seek medical care for upper respiratory infection?
- How is an upper respiratory infection diagnosed?
- What is the treatment for upper respiratory infection?
- What are some of the home remedies for upper respiratory infection?
- What are some data on alternative therapies in treating upper respiratory infections?
- What are the complications of an upper respiratory infection?
- Can an upper respiratory infection be prevented?
- What is the outlook for a patient suffering from an upper respiratory infection?
- Common Cold Prevention Slideshow
- Sinusitis Slideshow
- Take the Common Cold Quiz
- Find a local Family Physician in your town
Is an upper respiratory infection contagious?
A majority of upper respiratory infections are due to self-limited viral infections. Occasionally, bacterial infections may cause upper respiratory infections. Most often, upper respiratory infection is contagious and can spread from person to person by inhaling respiratory droplets from coughing or sneezing. The transmission can also occur by touching the nose or mouth by hand or other object exposed to the virus.
What are the causes of upper respiratory infection?
Upper respiratory infection is generally caused by the direct invasion of the inner lining (mucosa or mucus membrane) of the upper airway by the culprit virus or bacteria. In order for the pathogens (viruses and bacteria) to invade the mucus membrane of the upper airways, they have to fight through several physical and immunologic barriers.
The hair in the lining of the nose acts as physical barrier and can potentially trap the invading organisms. Additionally, the wet mucus inside the nasal cavity can engulf the viruses and bacteria that enter the upper airways. There are also small hair-like structures (cilia) that line the trachea which constantly move any foreign invaders up towards the pharynx to be eventually swallowed into the digestive tract and into the stomach.
In addition to these intense physical barriers in the upper respiratory tract, the immune system also does its part to fight the invasion of the pathogens or microbes entering the upper airway. Adenoids and tonsils located in the upper respiratory tract are a part of the immune system that help fight infections. Through the actions of the specialized cells, antibodies, and chemicals within these lymph nodes, invading microbes are engulfed within them and are eventually destroyed.
Despite these defense processes, invading viruses and bacteria adapt various mechanisms to resist destruction. They can sometimes produce toxins to impair the body's defense system or change their shape or outer structural proteins to disguise from being recognized by the immune systems (change of antigenicity). Some bacteria may produce adhesion factors that allow them to stick to the mucus membrane and hinder their destruction.
It is also important to note that different pathogens have varying ability to overcome the body's defense system and cause infections. Some viruses may infect by much fewer numbers than others.
Furthermore, different organisms require varying time of onset from when they enter the body to when symptoms occur (incubation time). Some of the common pathogens for upper respiratory infection and their respective incubation times are the following:
- rhinoviruses, 1-5 days;
- group A streptococci, 1-5 days;
- influenza and parainfluenza viruses, 1-4 days;
- respiratory syncytial virus (RSV), 7 days;
- pertussis (whooping cough), 7-21 days;
- diphtheria, 1-10 days; and
- Epstein-Barr virus (EBV), 4-6 weeks.
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