A friend of mine recently got onto a train and found a group of four seats that were empty except for one woman who was sitting face down. She looked asleep and he looked forward to a quiet journey. As soon as he sat down, the woman lifted her head to reveal streaming, puffy eyes and started sneezing profusely. This happened a few weeks after swine flu first began to dominate the headlines but being English, he was bound to the socially awkward choice of staying in his seat for the sake of avoiding social awkwardness.
Many of us probably have similar stories. At a time when fears of a flu pandemic dominate the headlines, does an innocuous sneeze make people fear the worst? Perhaps, but a new study suggests that hearing someone else sneeze plays with our minds far beyond exaggerated worries about pandemics. They can make us more worried about completely unrelated threats like heart attacks, crime and accidents. They can even affect our political attitudes.
On May 7, 2009, when swine flu had spread to at least 24 countries, a group of researchers from the University of Michigan took it upon themselves to sneeze in front of passers-by on their campus. Led by Spike Lee (no, not that one), the team approached 26 people who had heard the sneeze and 24 controls who hadn’t, and asked them to complete a questionnaire for a class project.
Compared to the control group, those who had heard the sneeze felt that “average Americans” were more likely to contract a serious disease, citing risks of 41% compared to just 27%. More surprisingly, they also gave significantly higher estimates for the risk of dying from a heart attack by the age of 50 or of dying from crime or accidents. They even had slightly less faith in US healthcare, although this difference wasn’t statistically significant.
Later on in the month, when almost twice as many countries had been infected, Lee performed a similar experiment in a shopping mall. This time, the experimenter asked passers-by to take part in a one-minute survey. Twenty-four of the volunteers received the form without much ado. Another 23 were handed the form by an experimenter who pretended to cough and sneeze at the same time, while covering her mouth with her forearm.
The first question asked people if they would prefer the federal government to allocate $1.3 billion towards the production of flu vaccines or the creation of green jobs. Faced with a sneezing, coughing researcher, almost half (48%) of the volunteers chose to finance the vaccine. Without the symptoms, only 17% did.
Of course, it’s possible that being handed a form by a spluttering individual just put the volunteers in a negative and grumpy mindset. But Lee thinks not – a second question about the general direction of the country showed that both groups of volunteers were, on the whole, equally ambivalent about it.
Lee suggests that a minor, everyday event (like a sneeze) can heighten our worries about a whole range of unrelated hazards because it brings to mind a prominent threat (like a flu pandemic). Our emotions are affected by our ability to assess risks, regardless of what those risks are. In this way, the feelings elicited by one threat can feed into our evaluation of others, and sneezing in a pandemic climate can make people more worried about unrelated hazards from heart disease to crime.
Obviously, there’s more work to be done. Lee’s team haven’t actually demonstrated that sneezing in a pandemic era makes people more worried about that specific threat. It would also be interesting to see if the effect they found waxes and wanes over time, and how that related to the amount of concurrent media coverage .
Nonetheless, one thing is clear. Like many aspects of our minds, people are completely unaware of this effect. When asked later, the volunteers didn’t twig to the aims of the experiments. And while they assumed that a sneeze could make them overestimate the risk of flu, they didn’t think it would make them think differently about the odds of other threats.
Reference: Psychological Science, in press.
More on our bizarre minds:
The prospect of infections spreading from animals to humans has become all too real with the onset of the current swine flu pandemic, and the threat of a bird flu still looming. But infections can jump the other way too. Decades before the world’s media were gripped with panic over bird flu, humans transferred a disease to chickens and it has since caused a poultry pandemic right under our noses.
The infection in question is a familiar one – Staphylococcus aureus, a common human bacterium that’s behind everything from mild skin infections to life-threatening MRSA. It causes chicken diseases too, including septic arthritis and ‘bumblefoot‘. But in the 1970s, broiler chickens began developing a new type of S.aureus infection called ‘bacterial chrondronecrosis with osteomyelitis’ or, more simply, BCO. It’s a bone infection and it’s a major cause of lameness in broiler chickens.
This new disease had human origins. Bethan Lowder from the University of Edinburgh has shown that all of the bacteria behind BCO share a common ancestor, which jumped from humans to chickens in Poland, around 38 years ago. From that point on, the bacterium’s travel itinerary was set. Just as air travel has facilitated the spread of swine flu among humans, a global distribution network for chickens made it easy for S.aureus to spread all over the world aboard its new feathery hosts.
Lowder traced the common ancestry of S.aureus in chickens by analysing the genes of 57 samples. Of these, 48 came from healthy and diseased chickens across eight countries and four continents, and 9 were taken from different species of wild and domesticated birds. Amazingly, she found that two-thirds of all the broiler chicken samples came from a single strain of the bacterium called ST5.
ST5 infects humans all over the world and is one of the most successful strains of S.aureus to do so. But Lowder found that all of the chicken samples were more closely related to each other than they were to any of the human bacteria from the same strain. They all shared a common ancestor – a lineage of ST5 found only in Poland. Around 38 years ago, this pioneering bacterium made the leap from humans to chickens and its descendants have spread from Poland to countries as far as the US and Japan.
Since then, the ST5 strain has adapted to its new host. It has lost many of the genes it needs to cause disease in humans but it has picked up others that allow it to better infect chickens. A complete sequence of the bacterium’s genome reveals that since its human days, it has picked up five new genes from other bird sources, none of which are found in humans or other mammals. In fact, Lowder thinks that the ST5 strain may be particularly good at picking up mobile genes from other sources. That might explain why both human and chicken versions are so successful, and why the human one often picks up genes that allow it to shrug off powerful antibiotics.
It’s not clear how exactly these changes benefit the bacteria, but certainly, they’re much better at resisting a chicken’s immune system than their human predecessors. When faced with chicken heterophils – a type of white blood cell – the poultry strains were much more likely to survive than the human equivalents.
Lowder thinks that globalisation was the key to the new pandemic. In just the last fifty years, the broiler chicken industry has shifted from one dominated by small farms to a multi-billion dollar leviathan controlled by a small number of multinationals. These companies transport a relatively few breeding lines of chickens all over the world, and the low genetic diversity of these birds makes them vulnerable to infections as opportunistic as S.aureus.
She recommends that livestock are screened regularly so that emerging diseases can be picked up, and that stocks should often be cleansed of S.aureus, to nip potential new threats in the bud. Better regulations for international transport wouldn’t go amiss either – it’s no surprise that Australia, a country with stringent regulations on importing livestock, has no trace of the pandemic S.aureus strain.
Reference: PNAS: 10.1073/pnas.0909285106
More on bacteria:
The swine flu pandemic (S-OIV) currently sweeping the world is the result of an influenza H1N1 virus that made the leap from pigs to humans. But this jump is just the latest leg of a journey that has taken over 90 years and shows no signs of finishing.
Today’s pandemic is a fourth-generation descendant of the 1918 flu virus that infected around a third of the world’s population. This original virus is an incredible survivor and one that has spawned a huge legacy of daughter viruses. By importing and exporting its genes, it has contributed to several new strains that have been responsible for at least three further pandemics, including the current one.
In an editorial in the New England Journal of Medicine, David Morens says, “We are living in a pandemic era that began around 1918.” This is one of two papers that narrate the incredible story of the 1918 virus and its descendants – a thrilling tale of survival, adaptation, extinction and resurrection.
All influenza A viruses contain 8 different genetic segments that they can freely exchange with one another. Morens beautifully compares each virus to a squad of eight players, rather than a single entity. For the viral team to be successful, its eight-person genetic team has to work together. Their individual skills become more or less useful with time and the team will often swap its members for fresh faces that add something new to the mix. In technical terms, they “reassort”.
To do that, viruses need to infect the same cell and they find communal ground in the internal passages of birds, pigs and humans. Animal bodies are essentially viral networking events where different squads can meet and exchange players.
In 1918, one such squad of players went on an infamous world tour. H1N1 influenza viruses had been around for a long time, but the story of the current “pandemic era” really begins in that year. While H1N1 was busy killing humans in our millions, pig farmers at the Cedar Rapids Swine Show in Iowa also noticed something unusual. Even though H1N1 had never been described in pigs before, their herds were suffering from an unusual respiratory illness, whose symptoms were very similar to those afflicting the world’s humans. Swine flu had landed.