At one time, infectious diseases used to decimate human populations — catching something such as cholera or smallpox was usually a death sentence.
But now, thanks to vaccines and antibiotics, few of us need worry about ‘catching’ anything worse than a cold, flu or an upset stomach.
But have we become too complacent?
Intriguingly, scientists are finding evidence that you may be able to catch such ‘lifestyle’ disorders as diabetes, Alzheimer’s and even joint pain
Intriguingly, scientists are finding evidence that you may be able to catch such ‘lifestyle’ disorders as diabetes, Alzheimer’s and even joint pain.
Last year, scientists found that bacteria from the gut that have been linked to conditions such as inflammatory bowel disease and allergies can form spores — tiny hibernating ‘seeds’ given off by live bacteria that help it survive and multiply.
The research, published in the journal Nature, showed these spores can survive in the open air and could potentially infect other people. ‘This is a new way of transmitting disease that hasn’t been considered before,’ said researchers at the Wellcome Trust Sanger Institute.
It’s cutting-edge science and, of course, more research is needed, but here we look at the surprising conditions researchers now believe might be infectious…
Earlier this year, U.S. researchers suggested that type 2 diabetes may be caught from damaged proteins known as prions — these are infectious agents, like those that transmitted BSE (or mad cow disease) from cattle to humans
CAN YOU PICK UP DIABETES FROM MEAT?
Earlier this year, U.S. researchers suggested that type 2 diabetes may be caught from damaged proteins known as prions — these are infectious agents, like those that transmitted BSE (or mad cow disease) from cattle to humans.
This is very different to the standard explanation for diabetes of too much weight and too little exercise leading to an excess of sugar (glucose) in the blood because the hormone insulin stops working correctly. The suggestion of ‘infectious’ diabetes may sound absurd at first, but a team at the University of Texas has found some striking evidence, published in The Journal of Experimental Medicine.
The researchers first found that most type 2 patients had clumps of damaged protein — known as IAPP — in their pancreas, the organ which produces insulin that is vital for keeping blood sugar at the right level.
Researchers have long known that damaged protein accumulates in the pancreas of diabetes patients, but they had generally assumed it was the result of the disease rather than a possible cause.
Then, and this is the crucial bit, the team injected IAPP into the pancreas of healthy mice and within a few weeks the mice also had too much blood sugar, and the insulin-producing beta cells in their pancreas were dying off.
It’s not definitive proof that diabetes can be caught, and it doesn’t necessarily mean diabetes can be spread like flu — prions don’t get passed on by contact or breathing them in — but the team is now investigating possible ways prions could infect humans, such as via blood transfusions or eating prion-infected meat.
‘Our data opens up an entirely new area of research,’ they said.
It is still only a theory, but with more evidence it could point to new ways to slow this rising epidemic. And it might help explain why some apparently slim, healthy people develop type 2 diabetes.
THE BUG LINKED TO ALZHEIMER’S
Despite scientists’ efforts, we still understand little about the cause — let alone cure — for several dreadful diseases that slowly destroy brain cells, such as Alzheimer’s or ALS (Amyotrophic lateral sclerosis, also known as motor neurone disease) which causes creeping and total paralysis.
Recently, however, a potential culprit has emerged — cyanobacteria, a close relative of algae, which creates blooms on lakes and ponds.
When in bloom, cyanobacteria contains a toxin, known as BMAA, that can damage the brain when it gets into the human body.
The cruel effect of BMAA was first spotted years ago when it was noted that inhabitants of the island of Guam in the Pacific had a high rate of a disease with symptoms similar to both Alzheimer’s and ALS.
Researchers made a link between eating the seeds of the cycad tree, now known to contain BMAA, and the disease.
Meanwhile, in the U.S. a neurologist identified ALS hotspots near lakes and wondered if cyanobacteria blooms on the water could be a factor.
It turned out that the air above a blooming lake was full of cyanobacteria in aerosol form, thrown up in the spray created by wind or boats, which could be inhaled. Then BMAA was found in diseased brains.
‘This research is in a very early stage,’ says Professor David Smith, a pharmacologist and Alzheimer’s researcher at Oxford University. ‘Other microbes have also been linked with Alzheimer’s, but the evidence is very limited.’
Earlier this year, however, scientists at the American Institute for Ethnomedicine reported that vervet monkeys given BMAA developed the plaques and tangles found in the brains of ALS and Alzheimer’s patients. A trial of an amino acid, which can partially block the effect of BMAA, is due to start soon at the Forbes Norris Research and Treatment Centre in San Francisco.
IS BEING OBESE INFECTIOUS?
This is an idea that’s been investigated for years by Dr Nikhil Dhurandhar, a professor of nutritional sciences at Texas University. He first identified a virus called SMAMI in India that seems to make chickens fat.
‘That was odd because viral infections usually cause weight loss,’ he is said. When he put infected chickens in with healthy ones, they also became overweight, even though they were eating exactly the same as before. Then he found that humans carrying SMAMI were likely to be heavier, with a higher BMI than those without it.
In the U.S., he found the same effect with one of the adenoviruses, called Ad-36, that normally cause nose and throat infections in humans.
This makes many animals, as well as humans, put on weight, possibly by increasing the amount of glucose they get from food or by making more fat molecules. He’s now working to develop a vaccine to prevent virus-induced obesity.
Furthermore, the team at the Wellcome Trust Sanger Institute, which discovered that human gut bacteria form ‘spores’ that could leave the body and survive in the outside world, has also pointed out that certain types of gut bacteria are linked to obesity.
Indeed, pioneering research in this area by U.S. scientists in 2006 showed that transplanting microbes from obese mice into healthy ones led to weight gain.
The theory is that ‘obese’ microbes could therefore get into other people and, in turn, make them more prone to weight gain.
The Wellcome researchers suggested airborne obesity microbes could be part of the reason why obesity tends to run in families (as well as genetics and lifestyle).
BACTERIA’S TIES TO ARTHRITIS
We generally think of arthritis as mainly affecting the joints of older people as the result of wear and tear, so there’s not much to be done other than try to reduce the swelling and pain.
Yet it may be that joint pain can be caused by various bacteria.
Among the bacteria most likely to affect the joints are staphylococcus, which are better known for causing skin and sinus problems; gonococcus — responsible for gonorrhoea; streptococcus that usually affects the skin and throat as well as causing meningitis and urinary tract infections; and pneumococcus which, along with pneumonia, also causes ear and sinus problems.
The thinking is that once you’ve caught an infection, even if this then clears up, the bacteria can travel to any joints in the body via the blood. It’s not clear why bacteria occasionally leave their normal target areas in this way.
More than 70 per cent of young children hospitalised with joint pain were found to have the same bug (Kingella kingae) in the joint and in their nose and throat, according to research from Geneva University Hospital published last month.
A useful clue that your painful joint is linked to an infection is that it flares up after you’ve already suffered from skin or sinus problems or a throat infection, for example. The painful joint normally responds to the usual antibiotic treatment.
Left untreated, the bacteria can quickly destroy parts of the joint and may cause blood poisoning.
Blood tests can detect if you have had a recent bacterial infection and an X-ray of the affected joint will show if it has been damaged.
So presuming you have wear-and-tear arthritis could be a painful mistake if the culprit was actually a bacterial infection, because you would miss out on treatments that would help.
SCHIZOPHRENIA FROM A CAT BUG
Parasites often have strange and complex life cycles.
One of the oddest is a tiny microbe only 5 microns long (by comparison, a human hair is around 75 microns thick) called Toxoplasma gondii, known as T. gondii or Toxo.
It can survive in soil, but can only reproduce inside a cat — spores are then distributed via cat faeces. Toxo has developed a remarkable way of increasing its chance of getting into cats by tinkering with the neurochemicals in the brains of mice. It extinguishes their fear of cats, making infected mice more likely to be caught by one.
Toxo can also infect humans via uncooked or ‘pink’ meat, unwashed vegetables, contact with infected soil or cat litter trays.
In most cases, infection won’t cause any symptoms, though sometimes it can lead to a flu-like illness.
However, some experts believe it can penetrate the brain — even if there is no other sign of infection — and that it is far from harmless.
Jaroslav Flegr, an evolutionary biologist at Charles University in Prague, is one of the researchers who believes Toxo can manipulate the chemistry of our brains, making some people more reckless.
Studies have linked infection to a higher chance of having a car crash, committing suicide and even developing schizophrenia.
A Toxo infection also seems to make it more likely you will develop a range of other disorders, especially ones in the joints and muscles, brain, immune system, lungs and digestive system.
Last year, in the journal Parasitology, Flegr commented that the parasite ‘represents a large and so far underrated public health problem’. While previous research has found an association between the parasite and risk-taking behaviour and mental illness, no direct effect on brain chemistry had been shown.
However, earlier this year, researchers at the University of California found that Toxo could trigger an increase in the brain chemical glutamate.
A small rise in glutamate levels can create an optimistic mood, but pushing it too high can damage brain cells, something that happens in brain disorders such as ALS, Alzheimer’s and depression.
The drug ketamine, which damps down glutamate, is currently being tested as an antidepressant.
COELIAC RISK FOR A PARTNER
We now know that the bacteria in our gut — our microbiome — can have a big impact on our health, including our immunity.
But could it also affect our risk of developing an auto-immune condition such as coeliac disease? The condition, which causes the immune system to react to gluten, a protein in wheat and other grains, is known to be genetically linked: first-degree relatives have a raised risk of it or other auto-immune diseases such as rheumatoid arthritis.
So it was a surprise two years ago when Swedish researchers analysing a big database found that the risk was also the same for the non-related family member — the husband or the wife.
They suggested sharing living conditions means sharing gut microbes and that this somehow primed them for the condition.
HOW YOUR OTHER HALF COULD BE MAKING YOU SICK
The marriage vows say ‘in sickness and in health’, but which is more likely if we share our lives with someone?
Close proximity may make us more likely to catch colds and flu, but a recent study found co-habitees pass on more useful bugs, too.
Couples soon begin to share some of their microbiome — the colony of 100 trillion microbes that live on the skin, genitals and in the gut.
Close proximity may make us more likely to catch colds and flu, but a recent study found co-habitees pass on more useful bugs, too
When scientists from the American Society for Microbiology took skin swabs from 20 people, their analysis correctly identified who lived together by matching types of bacteria found on their skin, particularly the feet.
This overlap could be handy, suggests Tim Spector, professor of genetic epidemiology at King’s College London.
‘The more diverse your microbiome, the healthier you are overall.
‘So the more you mix with others, the higher your chance of picking up valuable microbe strains you might not have.’ But we’re only likely to share around 10 per cent of our microbiome with our nearest and dearest, he adds.
‘Even identical twins only share 30 to 35 per cent of their microbes,’ he says.
‘The majority are unique to each person. Factors such as diet, shared space and having a family dog will contribute to the mix.
‘We’re not quite sure why, but it may be we get closer to dogs or perhaps that we have more similar microbes so they’re more easily transferred.’
‘And you’re more likely to see similarities on the skin, and the genitals if a couple is regularly intimate, than in the gut.’
So if you want to choose a partner to boost your health, avoid hygiene freaks (who might clean away beneficial bugs) and pick someone with a messy house, kids, a pet dog and a decent sex drive.
You could also do worse than choose a slim partner. ‘Studies have shown if you implant microbes from a thin mouse into the gut of another mouse, they have a protective effect against obesity, even if that mouse is then overfed,’ says Professor Spector.
‘I can’t promise that a thin partner will keep you slim, it’s still speculation, but it could play a part.’
Your partner may also influence your food choices.
A recent Polish study, reported in the journal Appetite, revealed couples who have been married for a long time develop similar preferences in taste and smell.
It’s thought that sharing the same meals over a period of years changes our perception of food and aroma and results in the same likes and dislikes, overriding genetic preference. Long-term partners also tend to develop matching kidney function, grip strength and total cholesterol according to an analysis of blood markers by the University of Michigan, presented last year at the annual meeting of the Gerontological Society of America.
‘Scientists call it “interpersonal synchronisation” — a phenomenon in which you begin to mirror the person you spend time with, on a psychological and physiological level,’ says Andrea Lindsay, a psychotherapist from clickfortherapy.com.
Interpersonal synchronicity could provide a novel way to tackle pain. A 2017 study by the University of Colorado and the University of Haifa in Israel, published in Scientific Reports, found that heart rates and breathing synchronise and pain dissipates if a couple touch when one partner is in pain.
‘The more empathic the partner and the stronger the analgesic effect, the higher the synchronisation between the two when they touch,’ said lead author Pavel Goldstein, a pain researcher at Colorado.
But the effects are not always equal between the sexes. For instance, larger women raise a man’s risk of type 2 diabetes, yet the reverse is not true.
This was the finding from a 17-year study by scientists at Aarhus University in Denmark that tracked 3,500 couples over 50. The results, presented at the annual meeting of the European Association for the Study of Diabetes last month, revealed that the woman’s weight at the start of the study was a strong predictor for her husband’s chance of developing type 2 diabetes, regardless of his weight.
For every extra five points a wife scored on the BMI scale, the husband was 21 per cent more likely to develop the condition. Yet a husband’s starting weight makes no difference to his wife’s chance of developing the disease.
Researchers suggest men are more influenced by their wives’ eating and activity patterns than vice versa, and women in this age group are more likely to cook the family meals.
In fact, men’s health seems to benefit from marriage, regardless of whether it makes them happy — a 2016 study by Michigan State University found a nagging wife can have a positive impact on her husband’s health, yet for women, health benefits come only from a happy marriage.