Introduction

Pertussis, possibly more commonly known as whooping cough, is a respiratory infection caused by the bacterium Bordetella pertussis. The common cold is also a respiratory infection caused by a variety of viruses. As they both affect the respiratory system, they may cause some similar symptoms, however, it is important to distinguish the two, due to the higher severity and danger of pertussis.  

What is pertussis?

Pertussis is an extremely contagious respiratory infection caused by Bordetella pertussis. It most commonly appears in babies, children, and adolescents, but adults are also able to fall victim to the disease. Younger children also tend to suffer from more serious symptoms, while adults experience a milder infection, mostly due to the action of the pertussis vaccine. Those who have not been vaccinated may also be at risk of more serious disease.¹

Transmission

Bordetella pertussis tends to be transmitted through small respiratory droplets released by coughing or sneezing. These will contain the bacterium and may be inhaled by others, infecting them also. A factor that contributes to the high transmissibility of pertussis, is that it may be spread by those infected before they get any symptoms, or up to 2 weeks after they seem to have stopped showing any symptoms. These people may therefore be spreading the bacterium unknowingly.² 

Symptoms

Symptoms of pertussis commonly start with:³

• A low-grade fever
• Runny nose
• Mild cough

After a week or so symptoms may develop to:³

• Coughing bouts
• A ‘whooping’ sound in between coughs.
• Thick mucus being brought up, which may cause vomiting.
• Becoming very red in the face.
• Babies may also have trouble breathing after coughing bouts and turn blue, or grey.

Complications

Complications are different in adults than in babies, with babies experiencing more severe complications. Babies may develop pneumonia, apnea (when breathing stops and then restarts repeatedly), convulsions, a brain disease called encephalopathy, and even death. Adults, on the other hand, may fracture their ribs from coughing so much, lose their bladder control, faint, or lose weight without meaning to.^1,3

The common cold

Causes

The common cold is caused by a variety of viruses, but most commonly rhinoviruses, which account for around 40% of all common colds. Other viruses which may also cause common colds are respiratory syncytial virus (RSV) and coronavirus. It is important to know that the coronaviruses that cause common colds are not the same as the virus, which causes Covid-19.⁴

Transmission

All of the viruses mentioned above are transmitted by droplets, expelled by infected individuals when coughing or sneezing. Rhinovirus and coronavirus are transmitted via the airborne route in small droplets, therefore, these droplets may be breathed in by others, causing infection. They may also settle on surfaces and cause infection if others touch those surfaces and then touch their eyes, nose, or mouth. RSV is transmitted by large droplets and is believed to use the mechanical transmission route. This means that the droplets settle on surfaces and when an individual touches those surfaces and then their eyes or nose, they may become infected.⁴ 

Symptoms

During the common cold, the following symptoms are commonly observed:⁵

• Cough
• Nasal symptoms like sneezing, congestion, or runny nose
• Hoarse voice
• Headache
• Bodyache
• Tiredness
• Fever (less common in adults)

Complications

Usually, a common cold is mild and goes away on its own within a week or two. However, there is a possibility of complications, especially in those who are immunocompromised. These include pneumonia, asthma flare-ups, sinus infections, and ear infections.^4,5 

Key differences between pertussis and the common cold

Cause

A large difference between the two illnesses is the causative agents. Pertussis is caused by a bacterium, whilst the common cold is caused by a virus. The two are very different microorganisms, bringing about infection in two distinct ways. The pertussis bacterium will bring about disease using toxins (‘poison’ made by bacteria that makes you ill), whilst the common cold viruses will bring about disease by invading, killing, or disrupting cells.^1,4,6 

Difference in symptoms

For pertussis, and the common cold, there are major differences in the symptoms. For the common cold, you usually will not develop a cough severe enough to last in long bouts, or cause ‘whooping’ noises, or produce vomit-inducing mucus. Also, for pertussis, you would be less likely to develop head or body aches. The duration of the symptoms may also be a good indicator as to what illness you may have. For the common cold, symptoms should not last longer than a week or two and the onset of peak symptoms is usually quite fast, occurring around the 4th day. Pertussis on the other hand becomes more serious after a week, or two, of milder infection and may last more than 10 weeks.^3,5 

Diagnosis and treatment

Diagnostic process

The diagnostic process for both diseases tends to be similar. They start with a physical exam carried out by a doctor, who should be able to determine what illness you have. For the common cold, this will usually be as far as it goes in terms of diagnosis. It is quite unlikely for the doctor to take a swab to send off to the laboratory, this would be more likely to occur if they suspect, e.g., Covid-19. If the doctor suspects common cold complications, they may order a chest X-ray to check for conditions like pneumonia. For pertussis, however, it is likely for the doctor to take a sample to send off for laboratory testing, to confirm the presence of Bordetella pertussis. They may obtain the sample by either using a swab on the inside of your nose, or by doing a saline flush of the nose, and back of the throat.^3,5 

Treatment

The treatments differ for the two conditions, considering they are caused, by different microorganisms. For pertussis, you will likely be given antibiotics if you are diagnosed within 3 weeks of the infection. If you are in a serious condition you will be hospitalised. For the common cold, there tends to not be any treatment administered, as most people overcome the disease naturally. Antibiotics must not be used for the common cold, as they do not work on viruses, but may contribute to antibiotic resistance. For both diseases, patients should stay well hydrated and rest.^3,5

Prevention

Pertussis vaccine

The most effective way to prevent pertussis is to receive the pertussis vaccine. This is the DTaP vaccine, which protects against diphtheria, tetanus, and pertussis. It is administered in five doses during early childhood, and it is recommended to get a booster during childhood.¹  

Hygiene

Hygiene is important to prevent the spread of the diseases. Good hygiene practices include:

• Washing hands with warm water, and soap, before eating and after using the toilet, or if unable to wash hands, use alcohol-based sanitisers
• Use tissues when coughing/sneezing, and dispose of them safely
• Avoid touching the face
• Sanitising frequently used surfaces

Limited exposure to infected individuals 

You should try not to come into contact with ill individuals and avoid hugging, kissing, or shaking hands. You also should not share utensils or water bottles with the infected person. If you are ill, you should stay home and avoid public spaces.^2,4 

Summary 

The two illnesses are respiratory infections caused by different types of organisms (bacteria for pertussis vs viruses for the common cold). Although pertussis and the common cold share some similar symptoms, they may be distinguished by the type of cough caused. Namely, the cough caused by pertussis will be more serious coming about in bouts, causing ‘whooping’ sounds in between, and pertussis may also cause mucus production, which may be vomit-inducing, which typically would not happen with the common cold. It is important to receive a diagnosis for pertussis promptly, as antibiotics are usually only administered to patients if they have been diagnosed within three weeks. The best way to prevent pertussis is by receiving the DTaP vaccine during childhood. Both illnesses may be prevented by good hygiene practices, and avoiding contact with those who are ill. If at any point, any of your symptoms start to get worse, or if your symptoms seem to persist, you should seek medical advice.