Most people think that whooping cough (pertussis) is a disease of children. It used to be, but not any more. In the developed world today where most children have received the vaccine in early life, 4 out of 5 confirmed cases are in teens and adults.
It was never exclusively a disease of children. Before immunization came along in the 1940s and 50s it was most common in children but it was common knowledge that adults occasionally got it too.
We now know that this is because the immunity that comes from getting whooping cough only lasts (approximately) 15 years.
During the 1950s whooping cough immunization became routine, and because it was very effective, the number of cases dropped so low that people forgot about its existence for the most part. The same happened with diphtheria and polio.
Although whooping cough is very unpleasant, in general it is only really serious for young children, especially infants who can easily die of it. Immunization drastically cut the death rate in children and the number of cases in older children. What nobody was aware of was that the vaccine, like the natural infection, only gave immunity for about 15 years.
A small number of people continued to get whooping cough but often went undiagnosed, especially after the 1980s when all the doctors who were familiar with it and knew how to diagnose it (3 weeks of paroxysmal coughing) had retired.
These ‘doldrum’ years when nobody was diagnosing whooping cough went on until after the millennium, but many people were still getting a mysterious choking cough with a feeling of suffocation and going blue. Even though it lasted up to 100 days, the cough never happened when they were seeing their doctor. They eventually recovered and forgot about it.
The turn around started about 2002 when a blood test was introduced for the disease. It would show up positive after 2 weeks of having the infection and was 90% accurate. Before this the only way of proving it was by culturing the causative bacterium, Bordetella pertussis.
Culture involved passing a swab to the back of the nose and sending it to a laboratory. It was such a tricky thing to get right that it was hardly ever attempted outside hospital, and even there, few people had the necessary skills to make it reliable. Not only that, the bugs had often gone by the time the diagnosis was suspected and the swab taken.
The blood test changed all that. Suddenly, suspected cases just needed a blood sample to be sent to the laboratory. Lo and behold, they mostly came back positive, so doctors started realising what these mysterious coughing illnesses were and tested more and more.
It took quite a long time for this change to happen as doctors were, and still are, to a large extent, unaware that adults get whooping cough. Many patients were diagnosing themselves from the internet and asking to be tested. That happened in the late noughties and now patients still often have to diagnose themselves, but testing is more readily done.
In addition to testing blood, it can now be done on oral fluid. This is very suitable for children and those scared of needles. Throat swabs can also be tested by PCR (polymerase chain reaction). This test actually came along at the same time as the blood test but was expensive then. Not any more, and it is available to GPs.
It is not surprising that as a result of all this new testing in developed countries the number of reported cases has gone up and up as people have realised that this disease is with us, and always has been.
The ability to do a blood test for recent infection by whooping cough has revealed that it is quite common to get infected with it without any noticeable symptoms. But it has the effect of boosting our immunity and explains why most people remain immune even though their jab has worn off.
Some people get mild symptoms that cannot be distinguished from any old cough and cold except with a blood test. A few, whose immune systems have failed to overcome the invader, get the full blown disease.
That takes the form of violent coughing attacks in which you feel like you are suffocating and gasping for air. Often associated with vomiting, sometimes a ‘whooping’ noise when breathing in, and occasionally fainting. These attack can happen just a few times a day, often in the night, or more than every hour. Between attacks everything is usually perfectly normal. The whole thing usually lasts from 3 weeks to 3 months.
Many people are calling the increase in cases over the last 15 years a resurgence of the disease and explaining it by blaming the change to acellular vaccine that was introduced around the millennium (like the blood test).
It is known that acellular vaccines (there are many sorts), do not give as long lasting protection as the old whole cell vaccines and may not be as good at stopping the infection being passed on, but if it fails, it does so by allowing the natural infection to take hold and boost immunity, probably largely unnoticed.
The ‘resurgence’ is better explained by the ability to now test for the disease and the increasing awareness among doctors that it is most usually seen in teens and adults rather than children.
There two messages here. The first is for people who do not normally have chest problems, who have a terrible cough that has been going on for at least 3 weeks but are otherwise well. Discuss with your doctor whether it might be worth getting tested for whooping cough.
The second message is for those who are pregnant. There is lots of whooping cough about. Babies are at risk of this potentially fatal disease before they get all their shots (about 4 months). A booster for whooping cough in mid pregnancy gives the baby almost complete protection and most antenatal care services are recommending and giving it. Get it. It is a no-brainer.
The picture at the top is of pertussis toxin, the main damaging poison produced by Bordetella pertussis. It looks pretty but it is killer stuff. The vaccine contains modified toxin that gives immunity to it.