The weather’s frosty, pine mist floats on the wind, and the distinctive aromas of cozy fireplaces, seasonal baking and hot cider fill the air. But winter’s scents aren’t the only things being spread.

Winter also marks the height of the respiratory virus season, a period of sniffles, sneezes, congestion, fever and other maladies brought about primarily by four pathogens: the respiratory syncytial virus (RSV) and the viruses that cause the common cold, COVID-19 and influenza.

It’s important to know the differences regarding these four seasonal diseases, including their cause, incubation period, symptoms, diagnosis, available vaccines and treatments.

Staying free from any of the four viruses relies on similar measures: frequent hand washing, wearing a mask, avoiding close contact with people who may already be infected, and sneezing or coughing into a disposable tissue.

For COVID-19, influenza and RSV, vaccines are the front line of defense, with doses given as recommended by the U.S. Centers for Disease Control and Prevention (CDC). There is no vaccine for the common cold.

Along with treatments specific to the individual illnesses, all patients can benefit from rest, keeping warm, increasing fluid intake and using over-the-counter (OTC) medications to ease congestion, sinus maladies, and aches and pains.

Media wishing to speak to Johns Hopkins Medicine experts about any or all of the four respiratory viruses should contact Michael Newman regarding the viruses in adults and Kim Polyniak regarding them in pediatric patients. The contact information for both media representatives is listed above.

For additional information on the four respiratory viruses, check out the following videos with Johns Hopkins Medicine infectious diseases experts Allison Agwu, M.D., S.C.M.; Lisa Maragakis, M.D.; and Aaron Milstone, M.D., M.H.S.:

• How do you prevent the spread of respiatory viruses?

• How do you know if you have a cold, COVID-19, the flu or RSV?

• When is it safe to leave the house after a respiratory illness?

COMMON COLD

• Caused by any one of more than 200 viruses; most frequently by rhinoviruses (“nose viruses”).
• The incubation period is from 12 hours to three days following infection. Besides being spread by airborne droplets from coughs or sneezes, infectious virus can be left on surfaces by a sick person.
• Symptoms include sore throat, sneezing, runny or stuffy nose, hacking coughs, mild fatigue and aches.
• Typically diagnosed by symptoms, and by ruling out other respiratory viruses through negative tests.
• Treatments include warm salt water gargling for a sore throat, petroleum jelly for chapped skin around the nose and lips, and warm steam for congestion.
• Myth about the common cold: “Colds are caused by exposure to cold weather or getting wet in the winter.”

CORONAVIRUS DISEASE 2019 (COVID-19)

• Caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
• Spread when an infected person releases droplets containing virus particles into the air. Studies indicate that infectious virus cannot be picked up from surfaces.
• Symptoms most commonly appear within a week after exposure to the virus. However, an infected person may show no symptoms at all and can still spread the virus.
• Symptoms may include fever or chills, congestion or runny nose, shortness of breath or difficulty breathing, new loss of taste or smell, diarrhea, muscle or body aches, and nausea or vomiting.
• Some symptoms may persist for months or years in a condition known as long COVID. This can lead to chronic illness requiring comprehensive care or causing disability.
• Diagnosed through either an at-home or practitioner-administered test.
• Vaccines are available and are updated as new strains of the virus emerge. Obtaining booster immunizations is strongly recommended.
• Treatments depend on severity of the illness and direction by your doctor. For mild COVID, rest and OTC fever-reducing medications may be sufficient. More severe cases may require hospitalization, with treatments that can include antiviral medicatios, supplemental oxygen, assisted ventilation and convalescent plasma (blood with antibodies against COVID-19 obtained from patients have been infected).
• Myth about COVID-19: “Having COVID once is enough to provide lifetime immunity.”

INFLUENZA (THE FLU)

• Caused by the influenza virus, which changes genetically year to year to present as a new strain.
• Symptoms typically appear one to four days after exposure to the virus, which is most commonly spread when an infected person releases droplets containing virus particles into the air. However, the flu virus can survive for short periods on surfaces that have been touched by an infected person.
• Symptoms may include coughing, extreme exhaustion, fatigue, headache, high fever, runny or stuffy nose, severe aches and pains, sneezing, sore throat, and vomiting and diarrhea.
• Fever and aches often last three to seven days. Coughing and fatigue may linger for two weeks or more.
• Diagnosed through either an at-home or practitioner-administered test.
• A vaccine, customized against the season’s specifc strain, is available each fall. A stronger-dose vaccine is available for people over age 65.
• Treatments depend on the severity of symptoms, as well as a person’s age and general health. Antiviral medications, as directed by your doctor, may be used to reduce severity, shorten illness duration and prevent complications (such as antibiotics to avoid secondary bacterial infections).
• Myth about influenza: “The flu vaccine can give people the flu in some cases.”

RESPIRATORY SYNCYTIAL VIRUS (RSV) INFECTION

• RSV infection is one of the most common respiratory diseases globally in children, and has become progressively more recognized as a vital pathogen in adults, particularly people over age 65.
• People of any age can contract RSV, but those at highest risk of complications are infants who are premature and children under age 2, infants under the age of 6 months, children under age 2 with chronic lung disease (such as asthma), children under age 2 with congenital heart problems, children with neuromuscular disorders (which make clearing mucus or swallowing difficult), children and adults with weakened immune systems, and older adults with heart or lung problems.
• Symptoms typically appear within four to six days after exposure to the virus, which is spread when an infected person releases droplets containing virus particles into the air.
• Symptoms may include runny nose, coughing, sneezing, wheezing, decreased appetite and low fever.
• RSV may lead to severe respiratory illness in infants. In these cases, symptoms may include high fever, worsening cough, wheezing, difficulty breathing, blue coloring of the lips and fingers, tiredness and trouble eating, drinking or swallowing.
• Lab tests may be used to help identify the virus.
• OTC medications may temper symptoms, but aspirin should not be given to children or teenagers. Severe symptoms may require hospitalization.
• Immunization for RSV has been available since 2023.
• Myth about RSV: “The virus only affects young children and is not a concern for adults.”