Cold & Viruses . What are they due to?

Colds and viruses increase every winter, as the lower the temperature, the greater the tendency for crowding indoors, making the transmission of the viruses responsible for colds and viruses much easier. The most common symptoms in colds and viruses that occur are:

• Fever
• runny nose
• cough

which can be caused by a variety of different viruses.

Which viruses have similar symptoms to colds and common viruses?

SaRs-CoV2

The coronavirus, known as SARS-CoV-2, causes the disease COVID-19. Possible symptoms of SARS-CoV-2 infection include the following:

• Fever
• Cough
• Fatigue
• Sore throat
• Runny Nose
• Myalgia
• Headache
• Difficulty in breathing
• Loss of taste or smell

The most common of these are fever, cough and fatigue, and the severity of these varies. Most people experience mild symptoms, while a percentage will develop serious complications that require medical attention. There are also cases in which patients do not show any symptoms, but can transmit the disease. The symptoms last for a few days or weeks, and sometimes even longer, causing “long-COVID”, which is still being studied.

From time to time the virus mutates, resulting in the prevalence of specific mutations over time, most recently the B.A.5 mutation, and the Centaur mutation (B.A.2.75), a sub-variant of the Omicron mutation. Symptomatology, however, has no significant differences between the existing mutations.

Influenza virus

The influenza virus (Influenza) can be divided into 4 categories: A, B, C, D, with the most common type being influenza A. Each type of flu is further divided into subtypes. Of these types, only types A and B can affect humans, which is why the flu vaccines that are renewed every year contain the common influenza A types, H1N1 and H3N2, as well as type B, which is milder. The common symptoms are:

• Fever
• Cough
• Sore throat
• Runny Nose
• Myalgia
• Headache
• Fatigue
• Vomiting
• Diarrhoea

Vomiting and diarrhoea occur more often in children than in adults, and symptoms last for about a week.

Common cold

The common cold can be caused by over 200 viruses, most commonly by rhinovirus. It is highly contagious and it is estimated that an adult will contract it up to 4 times each year, and children even more. It may be the cause of the following symptoms:

• Runny Nose
• Sore throat
• Cough
• Sneezing
• Wet eyes
• Fever

Fever is a rarer symptom in the case of the common cold and usually does not exceed 38°C, and overall, symptoms can last from 10 to 14 days.

Respiratory syncytial virus

Respiratory syncytial virus (RSV) is a common virus that causes infection of the respiratory tract. It is particularly common during infancy, as most children are affected by age 2. In children with congenital heart disease and premature infants, severe disease can occur, and can even lead to pneumonia and bronchiolitis. In contrast, adults usually present with symptoms resembling a mild cold, unless there are underlying conditions, a depressed immune system or an elderly patient, in which case the severity and risk of the disease increases. The most common symptoms, which disappear after 1-2 weeks, are the following:

• Fever
• Cough
• Runny Nose
• Loss of appetite
• Sneezing
• Breathing with wheezing

Adenoviruses

Adenoviruses are a large group of viruses with several subtypes that can cause febrile infections of the respiratory, gastrointestinal, ocular and rarely the nervous system. In healthy individuals, the adenovirus infection symptoms are mild. However, the same is not true for people with cardiac and respiratory diseases or with weakened immune systems, where the chances of severe disease are greater. Indicatively, the following are some of the occuring symptoms and complications:

• Fever
• Sore throat
• Bronchitis
• Pneumonia
• Conjunctivitis

What is the extent of the overlap between symptoms?

As can be seen from the above description of the most common viral infections, there is a great deal of overlap in symptoms. For SARS-COV-2, influenza and RSV the common core symptoms of fever and cough can lead to confusion as to which virus is responsible. COVID-19 is nevertheless differentiated by the loss of taste and smell that it can cause, while RSV is characterised by wheezing. The table below is a summary of the most common symptoms of these three viruses.

What else can cause similar symptoms?

In addition to viral causes, several flu-like symptoms can be the result of a bacterial infection. Streptococcus, for example, can cause an acute sore throat, which is its characteristic symptom, as well as fever, myalgia and headache. It is important in case of suspected strep infection to perform a strep test to confirm the cause of the symptoms, and to receive a different treatment, depending on the presence of viral or bacterial infection. Another condition caused by streptococcus is bacterial pneumonia, which again results in headaches and muscle aches as well as coughing, shortness of breath and malaise. Bacterial pneumonia is more serious than viral pneumonia, but these similar symptoms may not make its bacterial nature clear from the start. Other bacterial infections with similar symptoms, although less common, are Legionnaires’ disease, particularly the more mild clinical form (Pontiac fever) which resembles influenza, and pneumonias caused by bacterial species of the genera Chlamydia and Mycoplasma.

How reliable are the results?

For the correct diagnosis of the cause of the infection, a molecular PCR test can be performed, or in the case of COVID-19 and influenza, a rapid antigen test (Rapid test). Rapid tests are characterised by high specificity and lower sensitivity, i.e. it is more likely to be a false negative than a false positive. Indeed, in studies of the reliability of these tests in cases where multiple false positives were detected, the cause was identified as the production of a defective batch. Molecular tests (RT-PCR) on the other hand have much higher sensitivity, and it has been calculated that the probability of a false positive result is negligible. Therefore, these two types of tests in combination can confirm each other, especially if the subject is asymptomatic.