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Common cold: the story on HearLore | HearLore
Common cold
The common cold is the most frequent infectious disease in human history, yet it remains one of the most misunderstood ailments. While the average adult experiences two to three infections annually and children may suffer six to eight colds a year, the sheer ubiquity of the virus has led to a dangerous complacency. This is not merely a minor inconvenience; it is a global economic engine of loss, accounting for over 20 billion dollars in annual costs in the United States alone. The economic toll extends beyond the 75 to 100 million physician visits and the 22 to 189 million school days missed each year. When parents miss 126 million workdays to care for sick children and employees lose another 150 million days, the collective productivity of the nation stalls. Despite this massive impact, the disease has existed since the dawn of human civilization, with symptoms described in the Egyptian Ebers papyrus before the 16th century BCE, long before the name cold came into use in the 16th century due to the perceived link between weather and illness.
The Two Hundred Strains
The primary reason a vaccine for the common cold remains a scientific impossibility is the sheer diversity of the enemy. Well over 200 virus strains are implicated in causing the common cold, with enteroviruses, coronaviruses, and adenoviruses being the most common culprits. The most frequently implicated is the rhinovirus, a type of picornavirus with 99 known serotypes, which accounts for 30 to 80 percent of all cases. These viruses mutate rapidly and vary so widely that creating a broadly effective vaccine is highly improbable. In total, the viral cause of 20 to 30 percent of common colds remains unknown. This biological chaos means that immunity to one strain offers little protection against another, allowing the virus to circulate endlessly. The common cold virus can survive for prolonged periods in the environment, with rhinoviruses persisting for over 18 hours on surfaces, waiting to be picked up by hands and transferred to the eyes or nose.
The Body's Betrayal
The symptoms that define the common cold are not caused by the virus destroying tissue, but by the body's own immune system fighting back. The mechanism of this immune response is virus-specific, yet the result is universally recognizable: inflammation, congestion, and mucus. For example, the rhinovirus binds to humans via ICAM-1 receptors and the CDHR3 receptor to trigger the release of inflammatory mediators, which then produce the symptoms. It does not generally cause damage to the nasal epithelium, unlike the respiratory syncytial virus which replicates in the nose and throat before spreading to the lower respiratory tract and causing actual epithelium damage. The color of the mucus or nasal secretion may vary from clear to yellow to green, but this does not indicate the class of agent causing the infection. A sore throat is present in about 40 percent of cases, a cough in about 50 percent, and muscle aches in about 50 percent, all serving as signals of the immune system's internal battle rather than direct viral destruction.
What is the common cold and how frequently does it occur in adults and children?
The common cold is the most frequent infectious disease in human history and a viral infection of the upper respiratory tract. The average adult experiences two to three infections annually while children may suffer six to eight colds a year.
Why is there no vaccine for the common cold despite decades of research?
A vaccine for the common cold remains a scientific impossibility because well over 200 virus strains are implicated in causing the disease. The rhinovirus alone has 99 known serotypes and these viruses mutate rapidly and vary so widely that creating a broadly effective vaccine is highly improbable.
When was the Common Cold Unit established and what major discovery did it make?
The Common Cold Unit was set up by the Medical Research Council in the United Kingdom in 1946. It was here that the rhinovirus was discovered in 1956, marking a pivotal moment in understanding the disease.
How much does the common cold cost the United States economy each year?
The common cold accounts for over 20 billion dollars in annual costs in the United States alone. This figure includes 75 to 100 million physician visits and over 20 billion dollars in cold-related work loss which accounts for 40 percent of time lost from work.
Does cold weather cause the common cold or does it just increase transmission rates?
Normal exposure to cold does not increase one's risk of infection but severe exposure leading to significant reduction of body temperature known as hypothermia may put one at greater risk. The prevalence of many such viruses is indeed seasonal occurring more frequently during cold weather due to factors like low humidity and social shifts.
Can zinc supplements shorten the duration of a common cold and what are the risks?
Zinc supplements may shorten the duration of colds by up to 33 percent and reduce the severity of symptoms if supplementation begins within 24 hours of the onset of symptoms. However some zinc remedies directly applied to the inside of the nose have led to the loss of the sense of smell.
A common misconception is that one can catch a cold merely through prolonged exposure to cold weather, yet the prevalence of many such viruses is indeed seasonal, occurring more frequently during cold weather. The reason for this seasonality has not been conclusively determined, though possible explanations include cold temperature-induced changes in the respiratory system, decreased immune response, and low humidity causing an increase in viral transmission rates. Dry air allows small viral droplets to disperse farther and stay in the air longer, while social factors such as people spending more time indoors near infected people, and especially children at school, contribute to the spread. Although normal exposure to cold does not increase one's risk of infection, severe exposure leading to significant reduction of body temperature, known as hypothermia, may put one at a greater risk for the common cold. This paradox persists despite the fact that infections occur more commonly during the winter, and the apparent seasonality is often attributed to these environmental and social shifts rather than the temperature itself.
The Unit of Silence
In the United Kingdom, the Common Cold Unit was set up by the Medical Research Council in 1946, serving as the epicenter of cold research for decades. It was here that the rhinovirus was discovered in 1956, marking a pivotal moment in understanding the disease. The unit demonstrated that treatment with interferon during the incubation phase of rhinovirus infection protects somewhat against the disease, but no practical treatment could be developed. The unit was closed in 1989, two years after it completed research of zinc gluconate lozenges in the prevention and treatment of rhinovirus colds, the only successful treatment in the history of the unit. Despite the closure, the legacy of the unit remains in the understanding that antibiotics have no effect against viral infections, yet they are still frequently prescribed due to people's expectations and the difficulty in excluding complications. The unit's work highlighted the futility of trying to cure a disease that is so widespread and non-specific, leading to the conclusion that isolation or quarantine is not used.
The Zinc Gamble
Zinc supplements may shorten the duration of colds by up to 33 percent and reduce the severity of symptoms if supplementation begins within 24 hours of the onset of symptoms. However, the use of zinc is a double-edged sword, as some zinc remedies directly applied to the inside of the nose have led to the loss of the sense of smell. A 2017 review did not recommend the use of zinc for the common cold for various reasons, whereas a 2017 and 2018 review both recommended the use of zinc, but also advocated further research on the topic. The uncertainty surrounding zinc reflects the broader struggle with cold treatments, where much of the benefit from symptomatic treatment is attributed to the placebo effect. No medications or herbal remedies had been conclusively demonstrated to shorten the duration of infection, and the misuse of dextromethorphan, an over-the-counter cough medicine, has led to its ban in a number of countries. The lack of effective antiviral drugs for the common cold persists, even though some preliminary research has shown benefits, leaving patients to rely on rest, fluids, and the hope that symptoms will resolve in seven to ten days.
The Economic Toll
The economic impact of the common cold is not well understood in much of the world, yet in the United States, the common cold leads to 75 to 100 million physician visits annually at a conservative cost estimate of 7.7 billion dollars per year. Americans spend 2.9 billion dollars on over-the-counter drugs and another 400 million dollars on prescription medicines for symptom relief. More than one-third of people who saw a doctor received an antibiotic prescription, which has implications for antibiotic resistance. An estimated 22 to 189 million school days are missed annually due to a cold, and parents missed 126 million workdays to stay home to care for their children. When added to the 150 million workdays missed by employees who have a cold, the total economic impact of cold-related work loss exceeds 20 billion dollars per year. This accounts for 40 percent of time lost from work in the United States, making the common cold a silent economic crisis that affects every sector of society, from schools to corporations, without any vaccine or cure to stop it.