The common cold is a non-serious disease caused by several viruses. It affects the nose and throat and in most cases does not cause any harm, although it might seem otherwise, and viruses cause the cold. 
Adults are mostly infected with colds once or twice a year, while infants and children may be infected with colds more frequently. 
Most people recover from a cold within a period of 7 to 10 days; however, if the patient is a smoker, the symptoms may last longer. You will often not need medical care when infected with a cold, but if symptoms do not improve or if they worsen, consult a doctor. 
Cold viruses are transmitted by direct contact or through droplets, and the direct transmission of the virus is considered the most effective mechanism for rhinoviruses. 
The transmission of the virus from one person to another depends on the length of time the person spends next to the sick person and the amount of viruses present in the patient. 
Transmission by contact is the primary method of transmitting the infection; the virus is transmitted in contaminated saliva secretions from the patient to another person via the hands and from there to the nose and eyes. 
The virus can live for two hours on the skin and its presence has been shown in 40% - 90% of cold patients, and rhinoviruses are also transmitted by droplets. 
Symptoms of the Common Cold
The incubation period of the virus, from the occurrence of the infection until the onset of noticeable cold symptoms, ranges between 24 - 72 hours. 
Symptoms vary from one person to another and include: 
•    Runny nose and mucous congestion in the nose. 
•    Nasal blockage. 
•    Sneezing. 
•    Sore throat. 
Mostly, the sore throat disappears quickly, while the runny nose and congestion remain the primary source of complaint for patients, especially on the second and third days from the onset of the disease. On the fourth and fifth days, the cough becomes the primary source of annoyance, while the severity of other symptoms lessens. 
The cold usually lasts between 3 – 7 days, although it lasts for about two additional weeks in nearly a quarter of patients. 
The cold may be more difficult and severe in children, in people with chronic diseases, in people suffering from a defect in the functioning of the immune system, and in those suffering from malnutrition. 
Causes and Risk Factors of the Common Cold
There are many viruses that cause the common cold. 
Viruses causing the common cold
The following viruses cause cold infections: 
•    Rhinoviruses: cause 10% - 40% of cold cases. 
•    Respiratory syncytial virus (RSV): this type of virus causes 20% of disease cases. 
•    Coronaviruses: Coronaviruses cause 10% of cold infection cases. 
Viruses causing symptoms similar to the common cold
Some viruses cause symptoms similar to cold symptoms, but they are usually accompanied by pneumonia, or a more severe and dangerous disease, including: 
•    Influenza viruses. 
•    Adenoviruses. 
•    Parainfluenza. 
Also, some viruses cause symptoms similar to cold symptoms, but they do not usually lead to the appearance of characteristic symptoms, and are accompanied by a high temperature only, including: 
•    Echovirus. 
•    Coxsackievirus. 
Differentiating between types of viruses
It is difficult to identify and distinguish the causative virus based on symptoms alone, although parainfluenza infects children while the respiratory syncytial virus (RSV) causes a mild cold. 
Most respiratory viruses causing the cold can lead to the recurrence and reappearance of the disease upon re-exposure to the virus, but the disease is less severe in this case. 
Rhinoviruses and parainfluenza cause colds in the fall and at the end of spring, while adenoviruses, coronaviruses, and respiratory syncytial viruses cause the disease to appear in the winter and spring seasons; as for echoviruses and coxsackieviruses, they cause colds in the summer. 
The respiratory syncytial virus is a highly contagious virus, and infection with this virus usually occurs through droplets, although the virus survives for about an hour at a temperature of 37 degrees Celsius. 
In 90% of patients exhibiting symptoms, the virus is not found in the saliva, leading to the belief that the virus is not transmitted through kissing. 
Risk factors for the common cold
Risk factors that increase the risk of catching a cold include: 
•    Infants. 
•    Winter season. 
•    Smoking. 
•    Weak immunity. 
Complications of the Common Cold
Potential complications of catching a cold include: 
Sinusitis
Sinusitis occurs due to bacteria, and it happens in 0.5% - 2.5% of adults after a cold. Computed tomography scans have shown that this inflammation appears in 39% of those infected with a cold after a week. Characteristic symptoms of the inflammation: purulent discharge, headache, and continuous fever. 
Pneumonia
Primarily due to infection with the respiratory syncytial virus. 
Exacerbation of asthma
About 40% of asthma attacks result from a cold. 
Diagnosis of the Common Cold
Doctors can diagnose most cold patients based on symptoms, but if the doctor suspects a bacterial infection, they perform a chest X-ray to ensure there is no inflammation. 
Treatment of the Common Cold
Treatment of the common cold generally aims to alleviate the signs and symptoms of the disease only. 
Treatment for a cold includes the following medications: 
•    Antihistamines that can alleviate coughing and a runny nose. 
•    Medications to suppress coughing. 
•    Medications to relieve mucous congestion in the nose, which are often in the form of drops. 
It has been shown in a number of studies that treating the cold with zinc tablets along with vitamin C, and with herbs, can be beneficial and effective in treating cold symptoms. 
There is no need for treatment with antibiotics, as they have not proven effective in treating the common cold. 
The effectiveness of antiviral treatment, whether combined with anti-inflammatory drugs or without them, has been proven in alleviating symptoms for the patient and even shortening the duration of the disease. 
Prevention of the Common Cold
Methods of preventing the common cold include: 
•    Washing hands thoroughly with soap and water. 
•    Avoiding touching the face and eyes if hands are unwashed. 
•    Sterilizing surfaces periodically. 
•    Strengthening immunity through adequate sleep and playing sports.