Introduction

There are many respiratory illnesses, especially around the winter. Some of these illnesses include pertussis, also known as whooping cough and the flu, also known as influenza. It is essential to understand more about these respiratory illnesses and the impact they have on public health. In this manner, we will be able to understand the correlation between both diseases and look for preventative measures.

Pertussis was normally seen as a pediatric disease affecting mostly children with approximately 38% of cases being from babies younger than 6 months and 71% of cases showing in children younger than 5 years old.

Nevertheless, it is important to remember that adults are also at risk and can be infected with pertussis, due to things like waning of immunity over a certain time after having the vaccine as an infant. After the vaccination against pertussis was discovered, the cases drastically decreased from approximately 150,000 to 250,000 annual cases to 1010 cases in 1976.  However, worldwide pertussis is still an alarming disease with an estimate of over 24 million cases and approximately more than 160,000 deaths per year.¹

Overview of pertussis

Pertussis is a respiratory condition and was previously known to have a high mortality and morbidity rate. It was first described in 1578, but the causative bacteria, Bordetella pertussis, for this condition was only discovered in 1906. Before sufficient research had been conducted on this disease, there were a lot of deaths, especially in young children. The vaccine for pertussis was only later invented in the 1940s reducing the mortality rate.¹

Causes and transmission

Pertussis is caused by the Bordetella pertussis bacteria and is known to have a very high morbidity and mortality. One reason for this is due to the easy transmission of this pathogen between people through airborne particles including sneezes and coughs. Therefore, if you think you have this condition, it is always advisable to take precautionary measures such as covering your mouth before coughing or sneezing and if necessary using a facemask.¹
Whilst pertussis can be scary and very contagious, the good news about pertussis is that there have been vaccines developed over the years which can easily protect the person by boosting their immune system. Therefore, vaccinated people do not have to worry as pertussis only affects households that do not have immunity against this pathogen. Furthermore, it is important to note that the vaccine immunity can decrease to roughly up to 50%, 12 years after the original dose.¹

Symptoms and stages of pertussis

Once a person has acquired pertussis, there are various stages that they go through. After a person has acquired the disease, for the first 1-3 weeks, they go through the incubation period where the bacteria is adapting to the new host. The next stages which are more serious and are usually where the symptoms start to occur are known as the catarrhal, paroxysmal, and convalescent stages.¹

Catarrhal stage

The catarrhal stage is the first stage of infection and has similar symptoms to other respiratory conditions, especially upper respiratory tract infections like the common cold, sinus infection (sinusitis), and sore throat. This stage usually lasts for roughly one to two weeks and can be seen as the most infectious stage of the disease. Normally, infectious people will be coughing and sneezing increasing the likelihood of transmitting the bacteria.¹

Paroxysmal stage

The next stage, following the catarrhal stage, is called the paroxysmal stage and is where most infectious people will develop a more violent and vigorous cough. During this stage, the infectious person is likely to have respiratory problems. When the patient is coughing, there is a high probability of forceful inspiration resulting in a “whoop” sound which is where the name “whooping cough” is derived from.  These coughing episodes are more common during the night and can be accompanied by other symptoms like diarrhoea, or diaphoresis known as intensive sweating.¹

Convalescent stage

The convalescent stage is the last stage of whooping cough and can last from weeks to months depending on the person. During this stage, the person will let out the last few residual coughs. The disease can also worsen if the infected person acquires other respiratory diseases or upper respiratory tract infections.¹

Overview of the flu

Causes and transmission

The flu is caused by a virus known as influenza. Four different types of influenza viruses that can be contagious, especially when transmitted through cough or sneeze droplets. The morbidity of influenza is quite high and even though the mortality rate has declined, it is usual for people to take sick leave when infected. Nevertheless, mortality rates are still high for those with lung diseases and diabetes.²

Types and subtypes of influenza strain

• Influenza type A - Within influenza type A, there are two different subtypes known as hemagglutinin (H), and the neuraminidase (N) proteins which are on the surface of the virus
• Influenza type B - The most current influenza pandemics, were influenza type B
• Influenza type C - Influenza type C can cause infections in both humans and pigs and is also associated with infections in cattle.Influenza type D - Influenza type D also affects animals, in particular, cattle and other animals but it can also infect people^2,3,4

Symptoms and complications

According to the CDC, the most common symptoms of influenza are:

• Fever
• Cough
• Sore throat
• Stuffed nose
• Body aches
• Fatigue⁵

The symptoms highlighted above are the most common, however, in certain severe cases, the symptoms may exacerbate resulting in shortness of breath, tachycardia, pneumonia and low blood pressure (hypotension).²

Seasonal patterns and prevalence

The flu tends to come on an annual basis, typically around the winter months. The duration of the season varies from year to year. For example, in some years, it can begin in October whilst others begin from December till February. It is also good to note that the flu can even last until May. The variation of the flu season has been even more unpredictable since the beginning of Covid. In 2021, it was noted that there were more infections around February.⁶

Interaction between pertussis and the flu season

Coincidence of peak periods

Unlike the flu season, pertussis incidences are more varied, however, it has been reported that they occur between June and September and around the winter months.

This coincides with the influenza virus which normally infects people around winter months. Due to both diseases having overlapping symptoms, sometimes it can be difficult to distinguish one from another.

Due to the bad weather in winter, it is common for people to acquire these viruses and other respiratory conditions. A study proved that once someone acquires the pertussis virus, it can exacerbate the effects of the influenza virus. This is done mainly by increasing the number of viruses in the airways and enhancing mortality.^7,8

Public health implications

Vaccination strategies

Due to both influenza and pertussis infectious diseases, having high mortality rates and causing respiratory problems, vaccinations have been developed for both vaccines and are advised to get.

Pertussis vaccination

There are three doses of the pertussis vaccination, diphtheria-tetanus-pertussis (DTP3). Due to pertussis being an infectious disease common in children, it is advisable by the WHO, that infants of around 6 weeks of age, take the first dose and the subsequent doses to be given with a 4-8 week in-between period. In addition, booster doses are advised after a year.⁹

Flu vaccination (annual flu shot)

The flu vaccine is best administered every year as a booster. The booster dose is normally administered in autumn or early winter as the flu peak season is normally around the winter months. This flu jab will protect people especially those are higher risk from getting very ill if they do catch the flu. The NHS offers free flu jabs and prioritises people who are:

• Over 65 years old
• Pregnant 
• Have underlying health conditions
• Disabled
• A person who lives with someone with a weak immune system¹⁰

Prevention

Even though vaccinations are good preventative measures, they are not foolproof and sometimes people can get infected, therefore it is important to take preventative precautions such as self-isolation and getting quick treatment. If you ever suspect of having either pertussis or influenza virus it is always advisable to consult a healthcare professional who will be able to give good advice on the best course of treatment. 

Summary

Two of the most common infectious respiratory diseases are pertussis, also known as whooping cough, and the influenza virus, also known as the flu. These infectious diseases are very common to have high mortality rates, influence one another and show similar symptoms such as coughs, fevers, and sore throats. Most people have been immunised against these infectious diseases by having a vaccine. However, it is important to note that even being vaccinated, you can still catch the virus so it is always good to take preventative precautions and consult a healthcare professional should you suspect to have caught it.