NEW HAVEN, Conn. — When it comes to the spread of illness, children are often seen as little germ factories, bringing home colds and flus from school and daycare. But a new study suggests that kids, particularly those under 10, may also be responsible for spreading a more serious type of bacteria to their grandparents and other older adults in their lives.
The bacteria in question is Streptococcus pneumoniae, or pneumococcus for short. While this germ is a common cause of relatively mild illnesses like ear and sinus infections, it can also lead to much more severe diseases such as pneumonia, sepsis, and meningitis. In fact, pneumococcal infections claim nearly two million lives worldwide each year, with the elderly and children under two being most at risk.
The study, set to be presented at the European Congress of Clinical Microbiology and Infectious Diseases (ECCMID 2024) in Barcelona, Spain, sheds new light on how this dangerous bacteria might be making its way to older adults. “If substantial pneumococcal transmission occurs between adults, then vaccination of older adults could have the additional benefit of reducing transmission and potentially serious disease,” explains lead author Dr. Anne Wyllie from the Yale School of Public Health, in a media release.
Scientists Turn To Saliva Samples For Pneumococcus Detection
To understand more about this transmission, Dr. Wyllie and her team conducted a unique study over two autumn/winter seasons in New Haven. They enrolled 183 adults aged 60 and over, all of whom lived in households without any younger individuals. These participants, who had an average age of 70 and were mostly white and female, were part of 93 household pairs, typically married couples.
Every two weeks for a period of 10 weeks, the researchers collected saliva samples from the participants and had them fill out questionnaires about their social behaviors and health. The saliva samples were then tested for the presence of pneumococcal DNA using a method called quantitative PCR (qPCR). This allowed the researchers to not only detect the presence of the bacteria, but also to identify different strains.
Now, you might be wondering why the researchers chose to use saliva samples instead of the more common nasopharyngeal swabs (those long cotton swabs that go way back into your nose). It turns out that previous work by Dr. Wyllie had shown that these swabs often fail to detect pneumococcus in adults, whereas saliva samples are much more effective.
So, what did they find? Overall, about 5% of the saliva samples tested positive for pneumococcus, and 15% of the participants were found to be carrying the bacteria at least once during the study period. Interestingly, several individuals tested positive at multiple time points, with two participants carrying the bacteria throughout the entire 10-week period. In about 5% of the households, both members were carriers, though not always at the same time.
Significantly Higher Risk For Older Adults Who Frequently Spend Time With Young Children
But here’s where it gets really interesting. The researchers found that the prevalence of pneumococcus was six times higher among older adults who had daily or almost daily contact with children compared to those who had no contact with children at all. When they looked closer at the age of the children, they found that contact with kids under 10 was associated with the highest prevalence. In fact, those who had recent contact with children under 5 had a pneumococcal prevalence of nearly 15%, while those in contact with 5-9-year-olds had a prevalence of about 14%. In contrast, contact with children 10 and older was associated with a lower prevalence of around 8%.
The frequency of contact also seemed to matter. Older adults who had daily or almost daily contact with children had the highest prevalence at around 15-16%, while those who only had contact once or twice a month, or no contact at all, had much lower prevalence rates of 4.5% and 1.8% respectively.
But it’s not just about prevalence at a single point in time. The researchers also found that recent contact with children under 10 was associated with a three-fold increase in the rate of acquiring pneumococcus compared to no contact. And for those over-60s who had daily or almost daily contact with children, the risk of acquisition was a whopping six times higher than for those without any child contact.
Need For Adult Pneumococcal Vaccination
Interestingly, despite some households having an individual who tested positive for pneumococcus multiple times, and even instances where both adults in the household were carriers around the same time, the study found no clear evidence of adult-to-adult transmission.
“Instead, we found that transmission was highest among older adults who had frequent contact with young children,” says Dr. Wyllie. “This suggests that the main benefit of adult pneumococcal vaccination is to directly protect older adults who are exposed to children who may still carry and transmit some vaccine-type pneumococcal strains despite successful national childhood vaccination programs.”
It’s worth noting that this study took place during the COVID-19 pandemic, a time of strict transmission mitigation measures that eased over time. Despite a return to community activities and increased circulation of respiratory viruses in the second season of the study, pneumococcal carriage rates remained consistent.
The authors do point out some limitations of their study. It was a small, community-based study in one region of the U.S., involving mostly white, highly educated individuals. This might limit how applicable the findings are to other racial or ethnic groups and countries. They also note that while saliva is generally better for detecting pneumococcus in adults, they didn’t sample other sites in the upper airway, so the overall carriage prevalence might be underestimated.
Nonetheless, this study provides valuable insights into how a serious and potentially deadly bacteria might be making its way from the younger generation to the older, more vulnerable one. It highlights the importance of pneumococcal vaccination not just for children, but also for older adults, especially those who have frequent close contact with young kids.
So, while those hugs and kisses from little ones are priceless, it’s crucial that we also take steps to protect our older loved ones from the less visible but no less significant threats they might pose. Because when it comes to the health of our elders, an ounce of prevention is worth a pound of cure.