Introduction

Whooping cough is also known as pertussis. This infection records the highest number of deaths among diseases that have vaccines as prevention. The World Health Organization (WHO) has reported the number of deaths reaching 300 thousand annually worldwide with 90% of cases occurring in developing countries. The infection can strike people of any age while infants are at high risk of serious complications.

Causes & Transmission of Infection 

Pertussis infections are caused by the bacteria Bordetella pertussis which infects the airways that include the mouth, nose and throat. Humans are the only carriers of these bacteria. A person can be infected with pertussis after being in contact with a patient’s coughs, sneezes or water droplets containing the bacteria on surfaces. A patient with whooping cough can infect 12 to 15 other people if not isolated.

High-risk groups

●  Children without pertussis vaccine 

●  Pregnant women

●  Close contact with pertussis patients

Signs and Symptoms

Patients will usually show signs and symptoms after 10 - 14 days of being infected. The symptoms of this disease are divided into three phases.

1)   The 'catarrhal' phase

In the early stages, the patient will start with common symptoms such as fever, flu, cough, red eyes and fatigue. These symptoms will usually last for one to two weeks. Diagnosis is difficult at this phase due to its mild and nonspecific symptoms.

2)   The 'paroxysmal' phase

Next, the patient will enter the second stage, where the cough will change to the classic ‘whooping cough’, which is a repetitive coughing fit (described as paroxysmal coughing) followed by a 'whoop' sound when the patient struggles to breathe after coughing. The nature and sound of this cough cause this infection to be called whooping cough. These symptoms can last up to three months. The Classic Malay community named pertussis infection as the ‘100-day cough’. Patients also produce a lot of phlegm at this stage. Pertussis is one of the causes of bloody cough when the cough becomes serious. For babies, less than three months old, classic symptoms such as cough and 'whoop' sound are not usually portrayed. Babies usually do not cough but show symptoms such as shortness of breath until the face turns blue or purple and - to a certain extent - even stops breathing for a while. This lack of oxygen in this situation has increased the risk of death for newborns and infants.

3)   The ‘recovery’ phase 

The patient enters a stage of slow recovery after experiencing ‘whooping cough’ symptoms for several months. Symptoms will be much milder and accompanied by less frequent cough and 'whoop' sound.

Infectious period

Patients infected by pertussis are very contagious regardless of their current clinical phase. From the onset of the 'catarrhal phase’ up until the third week of the ‘paroxysmal phase’ they are deemed to be very contagious. However, the perceptible infectious rate is reduced 5 days after antibiotics are started.

Complications

1)   Adolescents and Adults

Adolescents and adults usually experience less serious symptoms of pertussis infection.

Most of the complications experienced are due to recurrent and strong coughs.

Among the complications of these coughs are as follows:

●  subconjunctival haemorrhage

●  bloody cough

●  loss of consciousness 

●  inguinal hernia

●  iron deficiency (due to vomiting after coughing)

2)   Infants

Babies especially under 6 months of age usually have more serious and potentially fatal complications.

●  Iron deficiency

o   Difficulty eating due to cough

●  Dehydration

o   Difficulty drinking due to cough

●  Seizure

o   Lack of oxygen to the brain caused by shortness of breath when coughing persists

●  Lung infection (pneumonia)

●  Brain damage (encephalopathy)

Diagnosis

Pertussis is difficult to detect at an early stage due to its mild symptoms such as a common fever that can be found in all sorts of infections and other conditions.

The following tests can help in the diagnosis:

●  Nasopharyngeal swab - swab will be inserted into the nasal cavity (up to the nasopharynx) to take a nasal sample

●  Blood test - to detect pertussis antibodies 

Treatment

It is very important to receive early treatment to avoid unwanted complications. Babies for example will usually receive intensive care - as these groups require careful attention - while adolescents and adults can receive treatment at home.

Erythromycin is effective against Bordetella pertussis. Antibiotics should be given as soon as possible to prevent the spread of the disease. Antibiotic treatment is also the most effective way to get rid of the notable whooping cough bacteria. Anyone with close contact with the disease (within three weeks) can take the antibiotic as a preventive measure.

Prevention

1)   Pertussis vaccine for infant

Vaccination is the most effective way to prevent whooping cough. Immunization coverage of more than 90 per cent of the community will establish a herd immunity that can prevent the spread of the disease. Conventionally, it is given through an injection that comprises pertussis, diphtheria and tetanus vaccine - given periodically according to the National Immunization Program Schedule. 

It’s also known by the name DTaP vaccine (Diphtheria, Tetanus, and Pertussis). The vaccine has an inactive form of toxin produced by bacteria that cause all three diseases. Vaccine injection thus enables the body to produce antibodies (without harming its host cell). A defensive mechanism that is able to fight future viral infection. In other words, antibodies are substances formed in the blood to destroy specific types of bacteria or viruses.

Notably, since November 2020, the Malaysian government has changed the pentavalent combination vaccine to an innovative hexavalent combination vaccine. According to experts, the hexavalent combination, also known as the six-series vaccine includes DTaP-IPV-HepB-Hib (Diphtheriae, Tetanus, Pertussis, Polio, Hepatitis B, Haemophilus Influenzae Type B) all in one shot, that will be administered via injection in three prime doses (at the age of 1 month, 2 month & 3 month) and one booster dose at 18 month. Think you know about vaccines? Take this quiz to find out!

The following table shows the dose and age for immunization of Pertussis (in conjunction with the six-series vaccination)

Table 1 Pertussis Immunization Schedule as stated in the National Immunization Program Schedule

One important reminder about vaccination is that newborns and infants having received the pertussis vaccine can still be infected by the disease. However, due to the antibody circulating their blood, the symptoms will be mild as compared to babies who do not receive the vaccine. Babies who receive the vaccine also have a lower risk of experiencing life-threatening complications such as shortness of breath and pale blue skin due to lack of oxygen.

2)   Pertussis vaccine for pregnant mother

As most pertussis cases involve infants under 3 months of age - who have yet to receive the vaccine - the Center for Disease Control and Prevention (CDC) recommends that corresponding vaccines be given to a woman for each pregnancy. This prevention can help because newborns do not have antibodies to protect them from whooping cough. Pregnant women who receive the vaccine, can produce and transmit these antibodies to the baby through the placenta in the womb. This method (passive immunity) can protect pregnant women as well as their beloved babies.

3) Ethics of coughing and sneezing

One should cover the mouth and nose with a tissue or handkerchief when sneezing or coughing. Practice handwashing with soap and water or sanitiser to prevent the spread of pertussis. Wear a nose and mouth cover or a mask if you are either susceptible to an infectious disease or a probable carrier.

Vaccine Side Effects Side

Common side effects after injection of Pertussis vaccine is:

●  Pain and swelling at the injection site

●  Fever

●  Vomiting

●  Loss of appetite

Most side effects are mild and can last from 1 to 3 days.

Conclusions

Pertussis is a serious and dangerous infection for children who do not have immunity over it. The disease can be prevented through vaccines. Therefore, parents should be alert of their children's injection schedule and always adhere to the vaccination appointments. Vaccines not only save your children but also others. Consult a doctor to know more about Pertussis vaccine.

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