The 10 Most Common Winter Illnesses

There are many illnesses that are common in winter. Almost all of them increase in prevalence due to the grouping of human beings in closed environments. Discover them!

Written and verified by el biólogo Samuel Antonio Sánchez Amador.

Last update: 06 February, 2024

Winter is a time of rest in closed places, as low temperatures prevent the carrying out of vertiginous or dangerous activities in the country, the beach, the mountains, and other environments. Although it seems ironic, there are common diseases in winter that increase the general mortality rate compared to the rest of the seasons of the year.

As indicated by the American Council of Science and Health, December, January, and February are the months with the highest mortality rate of the year, while during the summer, the death rate is considerably reduced in high-income countries. Do you want to know why? In the following article, we’ll show you the ten most common illnesses in winter and their pathological potential.

What are the most common winter illnesses?

Before entering fully into winter diseases, we want to take a moment to discover why, at this time of year, the mortality rate increases so much. We’ll summarize the possible reasons in the following list:

1. Heat waves are deadly, but cold waves are worse. In general terms, on an average winter day, the mortality rate is 15% higher than on a summer day. In addition, extremely low temperatures kill 20 times more than very high ones. Extreme cold is very dangerous.
2. Low temperatures favor the spread of viruses. In the following sections, we’ll explain this correlation.

As USA Today reports, of all weather-related deaths in Americans, 63% are from excessive cold exposure and hypothermia, while 31% are attributable to heat stroke. Without a doubt, the cold is more dangerous for humans. Discover with us ten common winter illnesses and their epidemiological burden.

1. The flu

Influenza is an infectious disease caused by influenza viruses A and B, both belonging to the Orthomyxoviridae family. The annual epidemiological outbreaks in winter occur due to influenza A, although the health significance of variants B, C, and D must be noted.

The microorganisms mentioned are viruses, and as such, they can’t reproduce on their own. Lacking the typical cellular replication machinery, they must invade the host’s cells, manufacture their genome with cellular ribosomes, and reproduce and multiply exponentially in a short time. This entire process (and the immune response) causes the symptoms of infection.

The incidence of influenza reaches an estimated 10-20% worldwide. That is, 1 in 5 people or 2 in 10 are experiencing a case of the flu at any given time and place. However, this value increases up to 40-60% in some age groups.

Beyond epidemiological figures, why does the incidence of flu infections increase during the winter? Harvard University proposes the following mechanisms:

1. During winter, people spend more time indoors with the windows closed. This favors the concentration of viruses in the environment and facilitates their transmission.
2. The days are shorter in winter. Therefore, we receive less sunlight, and the synthesis of vitamin D and melatonin is difficult. In a way, this could compromise the immune system a bit.
3. The virus stays in suspension longer when humidity is low and the air is light. If the relative humidity were very high at this time, the microorganisms would precipitate more quickly with the water vapor, and transmission thus would be reduced.

2. Common cold

The premise for the common cold is the same: As we spend more time indoors, viruses are transmitted more easily. In addition, the drying of the mucous membranes of the upper airways (due to low temperatures and wind) could favor the entry of pathogenic organisms more efficiently and easily.

Be that as it may, the cold is another of the ten most common winter illnesses. This infection of the upper respiratory tract is caused by different viruses, among which the following stand out: Rhinovirus, coronavirus, adenovirus, and even the aforementioned influenza viruses. Even so, it should be noted that the symptoms of the cold are much milder than those of the flu.

The probability of having a cold in winter is extremely high: Adults get sick from this viral group 2 to 6 times a year, while children do 6 to 10. Despite the mildness of the symptoms, this condition is the cause of 40% of work absenteeism and 30% of school absenteeism.

3. Asthma

Asthma is a chronic disease that causes the airways in the lungs to swell and narrow. This results in wheezing, coughing, shortness of breath, and other symptoms associated with a lack of oxygen. According to the European Respiratory Journal, 4.3% of the world population is asthmatic, although the figure is probably much higher.

For patients with this condition, winter can be the worst time of year. This is due to the following reasons:

1. In this season, the air is usually drier due to the action of the wind. When the respiratory tract is exposed to these conditions, the mucous membranes become dry, and irritation occurs. This symptomatology can be greatly exacerbated in people with asthma.
2. Asthma symptoms may worsen if the patient has a concomitant infection of the airways, such as a cold or the flu.
3. Exercise and physical activities are more demanding in the winter due to the cold and the wind. This overexertion can take a toll on people with asthma.

Asthma symptoms are the same in winter as in other seasons, but they can get worse in times of colder temperatures. Drinking plenty of water, breathing as much as possible through your nose, and always carrying your inhaler with you are good solutions to avoid chronic discomfort.

4. Conjunctivitis

Conjunctivitis is inflammation of the conjunctiva, a mucous membrane that covers the back of the eyelids and the front of the eyeball. The most common symptoms of this condition are redness, itching, “gritty” sensations in the eye, discharge, crusting, and excessive tearing.

Although it’s true that conjunctivitis can be caused by bacteria, fungi, parasites, allergens, foreign bodies, and chemicals, it’s estimated that 36% of the cases in adults have a clear viral origin. Adenoviruses, varicella-zoster virus, and herpes simplex are the main suspects.

The explanation of the prevalence of conjunctivitis in the winter is the same as that for colds and the flu: As we spend more time crowded together indoors, viral conjunctivitis can flare up in winter. Fortunately, this disease is self-limiting and usually resolves on its own within 1 to 3 weeks. To relieve symptoms, cold compresses can be placed on the affected eye.

5. Ear infections

Ear infections, specifically the otitis media type, are common winter illnesses. They usually occur as a direct consequence of a bad cold, especially in children between 3 months and 3 years of age, as indicated by the MSD Manuals portal. They’re more common at these ages because the ear structures of infants aren’t fully developed.

Adenoviruses, rhinoviruses, enteroviruses, and respiratory syncytial virus (RSV) are important in explaining the pathogenesis of otitis. Like viral conjunctivitis, this is usually a self-healing illness; that is, it resolves on its own in a few days. However, medications can be taken to relieve symptoms.

6. Strep throat

As its name suggests, strep throat is a bacterial infection that’s usually caused by group A Streptococcus. It can appear in people of all ages, although it’s most common in infants between 5 and 15 years of age. According to the Centers for Disease Control and Prevention (CDC), this disease has an epidemiological peak at two times of the year. Namely, winter and spring.

This illness appears with the following symptoms: Rapid-onset sore throat, odynophagia (pain when swallowing), fever, headache, abdominal discomfort, and vomiting, especially in young children. Antibiotics are necessary in this clinical picture, as they reduce the duration of symptoms, minimize transmission, and prevent complications.

7. Migraines

Migraines are very severe headaches that can appear with very worrisome symptoms, such as nausea, vomiting, and sensitivity to loud lights and sounds. Although the specific causes of this clinical picture haven’t yet been fully clarified, we know that that it arises from abnormal brain activity.

50% of the world’s population suffers from headaches once a year and 90% have experienced them at some point in their life. In any case, the global prevalence of migraines is somewhat lower, with a probability of suffering it throughout life of 18%. Based simply on its high incidence, it automatically becomes one of the most common winter illnesses.

As the Mayo Clinic indicates, in some people, climate changes can cause serotonergic imbalances, which are associated with the appearance of migraines. Cold-related triggers also worsen headache symptoms that may arise from any other cause.

8. Seasonal depression

Although it may not seem like it initially, seasonal affective disorder or depression is a recognized clinical entity, as shown by the United States National Library of Medicine. This psychiatric condition usually appears in late fall and early winter and usually ends when spring begins. Some of its symptoms are the following:

• Sadness and a gloomy outlook
• Feelings of hopelessness, irritation, and a pessimistic outlook
• Loss of interest in activities that were previously a source of excitement and well-being
• Low energy levels
• Sleeping too much or having trouble sleeping
• Weight gain
• Recurring suicidal thoughts

Although the exact causes of this disorder are unknown, it has been discovered that it could be linked to an imbalance of serotonin in the brain environment. The main treatment is phototherapy, as by recovering hours of light lost by the weather, the patient is expected to regain their normal state of mind.

9. Bronchitis

Bronchitis is a disease characterized by inflammation of the lining of the bronchi, structures that carry air to and from the lungs. Patients with this condition often cough up thick and discolored mucus, have difficulty breathing, manifest fatigue, experience chest discomfort, and may experience feverish symptoms.

Acute bronchitis is caused in 90% of cases by viral agents, which are spread by direct exposure to droplets emitted in coughs and sneezes by a sick person. Like the rest of the viral conditions on this list, its prevalence increases in winter due to coexistence in closed environments.

10. Sinus infections

Sinus infections, better known as sinusitis, occur when fluid builds up in the sinuses, cavities filled with air. Most of these conditions are viral in origin, although they can sometimes be attributed to bacterial infections.

Depending on the population group, sinusitis occurs in 15-40 inhabitants per 1000, and approximately 0.5% of respiratory infections are complicated by this condition. Some of the most common symptoms are a runny nose, nasal congestion, pain in the face, headache, bad breath, and coughing.

A group of illnesses with a common origin

The vast majority of the conditions cited here are of viral origin. All of them are common winter illnesses for a simple reason: Humans tend to group together indoors when it’s cold. Hence, the spread of pathogens through droplets and other airborne media is much easier.

Preventing these diseases is difficult, as living with other people implies exposure to common viral agents. In any case, almost all of them resolve on their own with a couple of days of rest and with the consumption of lots of fluids.