Common Viral Infections

Upper respiratory tract infections are most commonly caused by viruses. Viruses that can cause an upper respiratory tract infection include:

Rhinoviruses
Rhinovirus has an incubation time of one to five days, which means symptoms may occur between one and five days after exposure to the virus. Rhinoviruses are the most frequent cause of the common cold. They can also trigger asthma attacks and have been linked to sinusitis and ear infections. However, most rhinovirus infections resolve on their own within seven to 10 days and rarely lead to serious illness.

Influenza Viruses
Although influenza is considered a systemic infection rather than an upper respiratory infection, the influenza virus can cause a number of symptoms in the upper respiratory tract. There are two main types, or strains, of influenza virus: type A and type B. Influenza A and B viruses are responsible for seasonal flu epidemics every year. The flu can cause mild to severe illness, and at times can lead to death. The incubation time for influenza is one to four days, and people with the flu are most contagious in the first three to four days after symptoms develop.

Parainfluenza Viruses
Parainfluenza viruses, sometimes called human parainfluenza viruses or HPIVs, most commonly cause upper respiratory infections in infants, young children, older adults, and people with weakened immune systems. There are four types of HPIVs, and each one causes different symptoms and illnesses. Most people with HPIV illness recover on their own, but in some cases, serious illness, such as croup or pneumonia, can develop. The incubation time for HPIVs is usually two to seven days.

Coronaviruses
There are many different coronaviruses, and six of them are capable of infecting humans. The four most common coronaviruses typically cause mild to moderate upper respiratory tract infections, like the common cold. The two other types of coronaviruses, which are rare in the United States, can lead to serious illness and even death.

Respiratory Syncytial Virus (RSV)
Respiratory syncytial virus, or RSV, usually causes mild, cold-like symptoms. Most people recover in a week or two, but RSV can be serious, especially for infants and older adults. The incubation time for RSV is typically four to six days, and symptoms often appear in stages, not all at once. Most RSV infections go away on their own in a week or two.

Adenoviruses
In most cases, adenovirus infections are not severe. In addition to causing cold-like symptoms, adenoviruses can cause inflammation in the lower respiratory tract, diarrhea, and conjunctivitis, commonly called pink eye. Sometimes adenovirus can be shed, or released from the body, for a long time after a person recovers from an adenovirus infection.

Human Metapneumovirus
Human metapneumovirus can cause upper and lower respiratory illness in people of all ages. This virus is in the same family of viruses with RSV and measles. The incubation time is estimated to be three to six days.

Epstein-Barr Virus (EBV)
In addition to upper respiratory symptoms, Epstein-Barr virus, or EBV, commonly causes infectious mononucleosis, or mono. EBV spreads through bodily fluids, most commonly through saliva. Most people get infected with EBV at some point in their lives, but many never have any symptoms. When symptoms do present, they often last from weeks to months. Once a person is infected with EBV, the virus remains in the body in a latent, or inactive, state, and can reactivate and spread regardless of the time that has passed since the initial infection.