Stuffy nose is a term often used to refer to obstruction to the flow of air in and out of the nose, while runny nose refers to a discharge (fluid) coming from the nasal passages. Both of these conditions are associated with inflammation and swelling (congestion) of the inner lining of the nasal passages and sinuses. Rhinitis is a term that refers to inflammation of the nasal passages. A viral infection (the common cold) is the most common cause of a stuffy and/or runny nose, but allergies, influenza, other viral infections like RSV and sinus infections also may cause these symptoms and signs.

What is the killer cold virus?

Figure 1: Picture of a colorized transmission electron micrograph of adenovirus; SOURCE: CDC/Dr. G. William Gary, Jr.

The term "killer cold virus" was applied to a new strain of adenovirus (Adenoviridae) termed adenovirus 14, adenovirus type 14, or Ad14 that appeared in multiple outbreaks worldwide since the 1950s and that has caused severe pneumonia and deaths in several different groups of individuals. People use this term because typical adenoviruses cause symptoms of the common cold, not severe pneumonia or death in most people. Investigations are done by state and city health authorities, the U.S. Air Force, and CDC during several outbreaks showed that Ad14 is a rarely reported but emerging serotype of adenovirus that can cause severe and sometimes fatal respiratory disease in anyone, including healthy adults. In 2006, a 12-day-old died from Ad14. Fortunately, Ad14 infections are uncommon, and most infections from Ad14 strains are not serious; the severe or fatal outcomes from Ad14 are rare for this common cold virus. However, the name "killer cold virus" has stuck with the Ad14 strain of adenovirus infection. Health officials first identified the virus in the 1950s when adenoviruses were first isolated from human adenoids. (Adenovirus is named after adenoids.) The number 14 of Ad14 represents the antigenic makeup of the strain or type; currently, there are at least 52 strains (antigenically distinct) that immunologic techniques can distinguish. These viruses have a double-stranded DNA that lab experiments can easily modify and apparently can undergo changes in the environment that may change Ad14's ability to infect cells and cause disease. People infrequently report or encounter the Ad14 strain, while Ad4 and Ad7 strains are the most widespread adenovirus strains (account for about 80% of adenoviral infections).

Many different strains or types (serotypes) of viruses cause adenovirus infections. A human adenovirus occasionally may behave like Ad14 but usually produces a set of symptoms that is characteristic of that type or strain. For example, types 8, 9, 37, 53, and 54 can cause epidemic keratoconjunctivitis, while types 40 and 4 can cause gastroenteritis in children. However, in 2018, an outbreak of an Ad7 serotype was reported that acts like its close relative, Ad14, and has produced 11 deaths in a facility for children with serious pre-existing medical problems and the death of an 18-year-old college student with medical problems.