Influenza, gastroenteritis, and bronchiolitis are the main infections caused by winter viruses. These three conditions affect millions of people each year and place a heavy burden on healthcare systems during the winter. One of the challenges facing Santé publique France is to reduce the risk of transmission.

What are winter viruses?

Many viruses are present in winter. Respiratory viruses cause colds, nasopharyngitis, seasonal flu, bronchitis, and bronchiolitis in children. Meanwhile, the viruses responsible for gastroenteritis are most commonly known as “rotavirus” and “norovirus.”

How are these seasonal viruses transmitted?

Seasonal winter viruses are transmitted through various routes:

• Virus-laden droplets emitted when coughing or sneezing (which remain suspended in the air) or through droplets and saliva from people infected with a respiratory virus

• Direct contact between the hands of an infected person and another person (for example, by shaking hands) or through contact with objects (toys, stuffed animals, pacifiers, elevator buttons, cutlery, etc.) contaminated by a sick person

What are the health consequences of these viruses?

The main winter viral illnesses are the flu, gastroenteritis, and bronchiolitis. Each of these infections has its own set of symptoms. Usually, the flu strikes suddenly, presenting with a high fever, body aches, headaches, intense fatigue, general malaise, and respiratory symptoms (dry cough, runny nose). The illness lasts about a week, but fatigue is frequently felt for the next three or four weeks. A dry cough may persist for two weeks.

The flu is often considered a relatively harmless illness. This is most often the case when it affects young, healthy patients. However, the flu can be serious, even fatal, particularly in vulnerable individuals, such as the elderly, people with certain chronic conditions, pregnant women, those who are obese, or infants. Complications may then arise, such as:

• a severe lung infection (viral or bacterial pneumonia);

• worsening of an existing chronic condition (diabetes, chronic obstructive pulmonary disease, heart failure, chronic kidney disease, cystic fibrosis, etc.)

Bronchiolitis is caused by a virus that affects the lungs and causes swelling of the bronchioles (the smallest airways) in children under 2 years of age. This virus is very common and highly contagious. Infants’ bronchioles are smaller than those of children and adults. If an infant catches the virus, there is therefore a greater risk that the swelling of their bronchioles will block airflow.
Other winter viruses, such as the common cold in children or adults, can also trigger bronchiolitis in infants. The illness usually begins with a cold and a cough; then the child has trouble breathing and may have difficulty eating and drinking. Coughing fits are very common and may be accompanied by wheezing.

Gastroenteritis is an inflammation of the digestive tract, most often caused by viruses called “rotavirus” and “norovirus.” It can cause nausea, loss of appetite, vomiting, abdominal cramps, severe diarrhea (loose or watery stools, at least three times a day), dehydration, fever, extreme fatigue, and headaches. These viruses are common and highly contagious. Children under 5 years of age, especially infants, are highly susceptible to gastroenteritis: the younger the child, the greater the risk of dehydration (fluid loss through stools and vomiting). Older adults and people with chronic illnesses are also at higher risk of dehydration.

How can you protect yourself from winter viruses?

To reduce the risk of catching a winter virus, it is recommended to follow four preventive measures:

• Wear a disposable mask when in contact with the elderly, infants, people with chronic illnesses, or pregnant women. It is recommended to wear a disposable mask as soon as the first symptoms appear (fever, cough, sneezing).

• Wash your hands regularly with soap and water (preferably liquid) for 30 seconds, scrubbing your nails, fingertips, palms, the backs of your hands, wrists, and between your fingers. After washing, it is advisable to dry your hands with a clean towel or let them air dry. According to the World Health Organization (WHO), this is the most important hygiene measure for preventing the spread of infections. It is strongly recommended to wash your hands as often as possible, especially at times considered essential:

  • before and after caring for a baby

  • after visiting a sick person

  • before preparing, serving, or eating meals

  • after blowing your nose, coughing, or sneezing

  • after every time you go outside

  • after using public transportation (bus, coach, train, subway), upon arriving at the office or at home

  • after using the restroom.

The use of hand sanitizers (SHA) is effective at eliminating many transmissible microbes, but it is not effective against all germs. They should be used on hands that are visibly clean, as they disinfect but do not remove dirt from the hands.

• Use a disposable tissue to blow your nose, throw it in the trash, and then wash your hands. At home, a trash can with a lid is preferable

• Sneeze or cough into the crook of your elbow. If you cover your mouth and nose with your hand, the germs on your hand can spread to others through handshakes or by touching objects. If this is not possible (e.g., when holding a child), it is recommended to cover your mouth with a disposable tissue, throw it away, and then wash your hands. After coughing or sneezing into your hands, wash your hands as soon as possible to avoid contaminating people or objects.