The bacteria which causes whooping cough can “lurk silently” in the noses and throats of healthy people, researchers in the UK have discovered.
The hiding bacteria means that people can unknowingly transmit the infection to other people leading to sporadic outbreaks of the condition, according to medics at University Hospital Southampton (UHS).
Whooping cough, also known as pertussis, is a highly-contagious bacterial infection which is spread through the coughs and sneezes of an infected person.
It causes repeated coughing that can last for two to three months or more and affects around 16 million people every year worldwide, particularly in developing countries, causing about 200,000 preventable deaths in children.
The researchers at UHS, led by Professor Robert Read, inoculated 34 human volunteers with Bordetella pertussis via nose drops and monitored them in a research facility for 17 days.
They assessed their immune responses before giving them an antibiotic to clear the infection.
The results, published in the journal Clinical Infectious Diseases, state that participants could be safely infected without developing symptoms and cleared of the bacteria within two days.
Professor Read, director of the NIHR Southampton Biomedical Research Centre, said: “The study showed that the bacterium which causes whooping cough can lurk silently in the nose and throat of even healthy members of the community.
“This is extremely important as it explains why we are seeing episodic outbreaks of whooping cough throughout the world, with serious disease occurring in those people who are not vaccinated or who had their vaccines a long time ago.”
There were 25,891 cases of whooping cough diagnosed in the UK between 2012 and 2018 compared to 6,216 between 2005 and 2011 – a four-fold increase, according to UHS.
A UHS spokesman said: “Adults suffer a milder form of the disease compared to young children but can still have an unpleasant cough for up to three months, while babies under the age of six months can be vulnerable to severe and life-threatening complications.
“Although a vaccine is offered to all babies in the UK – where 18 have died as a result of the infection since 2012 – it does not offer lifelong protection and is now less effective than it was 15 years ago.
“This is why the Southampton discovery is so significant – it means the bacteria can spread from person to person, silently, and cause disease in those who are not immune, including babies, and those not vaccinated.”
The €2.7m study forms part of a wider €28m European project, PERISCOPE, funded by the Bill & Melinda Gates Foundation and the Innovative Medicines Initiative (IMI), involving experts from 22 institutions across 11 countries.