Category: Health

How can we prevent or delay Alzheimer’s?

“How can we push back or prevent Alzheimer’s?” asks Claudette in Quebec City. As with most health-related issues, the answer is we can do our best with diet and exercise. The Globe’s dietitian wrote a piece this week that outlined a new diet that may help stave off Alzheimer’s:

According to a study, a hybrid of these two eating plans – called the MIND diet – is associated with a significantly lower risk of developing Alzheimer’s disease. That’s true even if you don’t follow the diet strictly.

Along with elements from the Mediterranean and DASH diets, the MIND diet includes specific foods and nutrients found in past studies to be linked to optimal brain health. The diet’s 10 “brain-healthy food groups” include green leafy vegetables, other vegetables, berries, nuts, beans, whole grains, fish, poultry, olive oil and wine.

The plan also advises that five unhealthy food groups – red meat, butter and stick margarine, cheese (because of its high saturated-fat content), pastries and sweets, and fried or fast food – be limited.

The findings also hinted that the longer a person follows the MIND diet, the greater the protection from Alzheimer’s disease.

While this observational study shows promise for reducing the risk of Alzheimer’s, it doesn’t prove cause and effect. The results need to be confirmed by randomized controlled trials, the gold-standard evidence for a cause-and-effect relationship.

These new findings add to a growing body of evidence that strongly suggests your overall dietary pattern matters more than single nutrients when it comes to Alzheimer’s prevention.

Eating a combination of healthful foods that deliver a wide range of protective nutrients while, at the same time, minimizing your intake of foods that may harm brain cells is what counts.

Read the entire article – including the specifics o the MIND diet – here.  In a December 2014 article, The Globe’s fitness expert Alex Hutchison wrote about U.S. research that studied 150,000 participants and showed, “regular exercise lowers the risk of dying from Alzheimer’s by as much as 40 per cent – an indication that the disease’s progression is not unchangeable.”

“Currently, doctors do not screen for Alzheimer’s disease susceptibility because of the belief that nothing can be done for those at risk,” says Dr. Paul Williams, a staff scientist at Lawrence Berkeley National Laboratory in California and the author of the study. “However, our results add to the growing body of scientific evidence suggesting that people can be proactive in lowering Alzheimer’s disease risk.”

The results also showed that running and walking are equally effective as long as you burn the same amount of energy overall. That means you need to spend about twice as much time (or cover 50 per cent more distance) walking briskly compared to running, Williams says.

That doesn’t mean that lesser amounts of exercise are useless, cautions Dr. Jordan Antflick of the Ontario Brain Institute, who co-ordinated a 2013 report on the role of exercise in Alzheimer’s prevention and treatment.

“You don’t have to run a marathon,” he says. “Even raking the leaves or going for a walk after dinner can help.”

After reviewing more than 800 studies and selecting the 45 highest-quality trials, Antflick and his colleagues concluded that more than one in seven cases of Alzheimer’s could be prevented if everyone simply met the minimum guidelines of 150 minutes of exercise per week, in doses as short as 10 minutes at a time. Given that approximately 10 per cent of Canadians over 65 have Alzheimer’s, that would save tens or even hundreds of millions of dollars in health-care costs.

Read more from The Globe’s Health & Fitness section, and follow us on Twitter

How much naturally-occurring sugar (i.e. from fruit or milk) is healthy to eat?

Reader Lise Gleasure in Calgary asks, “I’ve been trying to reduce my added sugar (i.e. pop, candy) intake to improve health. How much naturally-occurring sugar (i.e. from fruit or milk) is healthy to eat?” Globe Health columnist and registered dietitian Leslie Beck has the answer:

There are no guidelines to limit natural sugars in fresh fruits and vegetables and milk because there is simply no evidence that consuming these sugars is harmful to our health.

Earlier this year, the World Health Organization (WHO) released strict limits for added sugars – those that are added to foods during processing. WHO called for adults to cut their intake to less then 10 per cent of daily calories or, even better, less than 5 per cent. For a standard 2000-calorie diet, these limits translate to no more than 50 grams (10 per cent calories) and 25 grams (5 per cent calories).

These new guidelines are based on evidence reducing added sugar intake to less than 10 per cent of daily calories helps guards against overweight and obesity. The WHO defined added sugars as those “added during processing, at home, and sugars naturally present in honey, syrups, fruit juices and fruit juice concentrates”.

But unlike added sugars, there are no specific intake guidelines for natural sugars which occur in fresh fruit and vegetables (called fructose) and milk and yogurt (called lactose).

You might wonder why fruit juice, which contains naturally-occurring sugar (not added sugar) needs to be limited along with other added sugars.  While pure fruit juice does deliver vitamins and minerals, it can be high in natural sugar. One cup of orange juice has 23 grams of sugar while one medium orange has 12 grams. And fruit juice has none of the fibre whole fruit does, so it doesn’t fill you up.  The extra calories from sugar in fruit juice can, therefore, lead to unwanted weight gain if you drink it regularly to quench your thirst.

Current dietary guidelines recommend that total carbohydrates can make up 45 to 65 per cent of your total daily calories.  If you eat, say, 1800 calories per day that means you can consume 202 to 292 grams of carbohydrates each day.

The majority of your carb grams will come from naturally-occurring sugars in fruit and vegetables and starches in foods like whole grains, starchy vegetables and beans and lentils.

The smallest contributor to your total carbohydrate intake – less than 10 per cent of your daily calories – should be added sugars.

Follow Leslie Beck on Twitter, read more from The Globe’s Health & Fitness section here, and revisit this piece from our archives: Are bananas making you fat?


Does smoking marijuana pose a lung cancer risk?

Reader Jim Roberts from Kincardine, Ont. asks: “Does smoking marijuana pose a lung cancer risk?” The answer is… complicated. Globe reporter Josh O’Kane – who spent a previous life in chemistry journal stacks, and occasionally moonlights in peer-reviewed journals – dove into recent research. O’Kane has this to say:

We’ve known for a long time that cigarettes cause lung cancer. Marijuana smoke has been found to have similar carcinogens as tobacco smoke, but that hardly tells the whole story. Even though the chemicals are there, there is little evidence of pot smoke having a causal relationship with lung cancer. Researchers have been trying to understand the connection, but it’s been a difficult process to establish a link.

That’s unfortunate, because as more jurisdictions decriminalize or even fully legalize the drug, its relationship with lung cancer is unfurling as an important public health matter. Knowing that, the Canadian Medical Association says this:

“Chronic [marijuana] users often have shortness of breath after exercise, coughing and chest tightness. It is probably associated with bronchitis and emphysema and may have risks for chronic lung disease and lung cancer, comparable to cigarette smoking. This is less of a problem for those that use vaporizers, as a harm reduction strategy.”

The science community has struggled to wrangle enough people together for a study who: a) are willing to be honest about how much they smoke, when in many jurisdictions it’s either criminalized, or, at best, still taboo; b) represent a wide range of marijuana smoking habits, from light to heavy, man. But there’s another big barrier to designing high-quality studies: cigarettes tend to muck up the details. Someone who smokes weed heavily may also smoke cigarettes, making it difficult to say what’s actually responsible if that person got a lung cancer diagnosis.

Canadians are behind some of the latest studies to try to wrestle with this mess. Most recently, researchers at the Lunenfeld-Tanenbaum Research Institute, at Toronto’s Mount Sinai Hospital, published a paper last year in the International Journal of Cancer that analyzes what it purports to be the “largest data set on cannabis and lung cancer risk to date.”

Read more

There’s an apple that will never brown for sale in Canada. What health risks do GMO foods pose?

Paul Marck, a reader in Kelowna, B.C., asks “The non-browning Arctic Apple is now approved for sale in Canada. Is there any science suggesting GMO foods pose risk to human health or envrionmental risks? And is there a risk they will contaminate non-GMO fruits?”  The Globe’s Dave McGinn responds:

The Arctic apple, engineered to be non-browning, became the latest genetically modified food to be approved by Health Canada this week. We’ll likely start seeing it in stores in 2017, according to Neal Carter, founder of Okanagan Specialty Fruits Inc., the British Columbia-based company that created the apple.

While there are a small number of scientific studies suggesting that these foods pose risks to human health and the environment, the overwhelming scientific consensus is that they are as safe as any other conventional food. Health Canada, the World Health Organization, the U.S. Academy of Sciences and the American Medical Association all endorse that view.

GMO crops have been part of our lives for more than two decades. The first such crop was approved by the U.S. Food and Drug Administration in 1994.

They have proliferated ever since. More than 120 genetically modified foods have been approved for sale in Canada. These range from insect resistant soy to virus resistant squash. (The complete list of “Novel Foods” approved by Health Canada can be found here.)

In explaining its approval of the Arctic apple, Health Canada provided this statement: “A gene was introduced into the Arctic apple that results in reduction in the levels of enzymes that make apples turn brown when sliced. In every other way, the Arctic apple tree and its fruits are identical to any other apple.”

The statement goes on to say that a thorough review was conducted by scientists with expertise in molecular biology, microbiology, toxicology, chemistry and nutrition.

“Following this assessment, it was determined that the changes made to the apple did not pose a greater risk to human health than apples currently available on the Canadian market,” it said. “In addition, Health Canada also concluded that the Arctic apple would have no impact on allergies, and that there are no differences in the nutritional value of the Arctic apple compared to other traditional apple varieties available for consumption.”

While there are a small number of studies that have suggested GMO foods do pose health risks, including linking GM corn to cancer in rats, or that DNA from GM crops can be transferred to humans who eat them, most of these studies have either been retracted, published in non-peer reviewed journals or questioned by independent scientists.

Meanwhile, there are more than 2, 000 studies that have concluded GMO foods pose no greater health risk than convention or organic foods.

“In order to maintain the position that GMOs are not adequately tested, or that they are harmful or risky, you have to either highly selectively cherry pick a few outliers of low scientific quality, or you have to simply deny the science,” Steven Novella, an assistant professor at the Yale University school of medicine, has written.

However, there is evidence to suggest that genes from GMO crops can migrate to non-GMO crops, as noted by the World Health Organization. (The WHO and other organizations refer to this as “outcrossing,” rather than the loaded term “contaminate.”) Separating GM crops from conventional crops is one way to address this problem.

Many people who oppose genetically modified food, including David Suzuki, argue that we still do not know their long term health effects. After all, these foods have only been part of our diet since 1994.

By its very nature, this is objection is difficult if not impossible to address without getting caught in an unproductive line of reasoning: Thousands of studies say these foods don’t pose a health risk, but on a long enough timeline they just might. Okay, but thousands of studies say they’re fine.

One way out of this is to label GMO foods. That way, supporters of labelling argue, those who are skeptical or simply don’t wish to consume GMOs would be able to exercise choice at the grocery store. Suzuki has called this a “basic right to choice.”

More than 60 countries currently require such labelling – and Canada is not one of them. Why? The government has said it does not mandate labelling because there are no known health risks to eating GM foods.

Do consumers nevertheless deserve labels in order to make informed decisions? That is a whole other question.

Follow Dave McGinn on Twitter and read more from Globe Health

Why are there are no seat belts in buses? (My 8-year-old asks)

The inquisitive eight-year-old daughter of Mike Kim, a reader in Markham, Ontario wants to know: “How come there are no seat belts in school buses?”  Globe Drive recently found the answer to this puzzling question: That buses are relatively safe, and seat belts may make them less so:

“Transport Canada and the provinces do not require school buses to have seat belts,” Roxane Marchand, senior media advisor with the agency, said in an email statement. “This is because compartmentalization — high-backed seats that are padded and closely spaced together — protects passengers in a crash.”

David Carroll, Legislation and Safety Consultant to the Ontario School Bus Association says that the compartment style of the bus means “There’s not a lot of room between seats and that’s to reduce acceleration in a collision.”

School buses are relatively safe vehicles as they are:

There were 3,684 injuries and 11 deaths in crashes on school buses in Canada between 2003 to 2012, Transport Canada notes in their National Collision Database.

In the same period, there were nearly 1.34 million injuries and 22,397 deaths in crashes on Canadian roads in all other vehicles.

And the addition of seat belts may make the compartmentalization of the school bus structure less safe:

 If there are seat belts on a school bus, Transport Canada recommends three-point belts — the harness and lap belt combination seen in most cars. But seats would have to be redesigned to have stiffer seat backs to support the shoulder belts.

“With firmer seat backs, you no longer have the same protection in that compartment,” Carroll said. “So any kids who aren’t wearing seat belts won’t be as protected in a crash as they are now.”

But these policies may change: In the U.S., rules will soon change for new motor coaches – like the ones used by Greyhound:

The National Highway Transportation Safety Administration  will be requiring seat belts on all newly built motor coaches, and  Transport Canada says it’s drafting regulations to follow suit.

Those new rules don’t affect school buses — but that could eventually change.

This month, the new head of NHTSA, convened a group to study whether seat belts should be mandatory on all school buses.

Follow Globe Drive on Twitter and read the full answer here


What’s the current recommendation about eggs? How many should I eat per day?

In Yellowknife, reader Sarah Mann asks:  “What’s the new recommendation about eggs?  How many can we eat per day?”  Globe Health columnist and registered dietitian Leslie Beck says, “eggs have long been vilified for their high cholesterol content. One large egg has 183 milligrams of cholesterol, almost two-thirds of a day’s worth for healthy people.” She says a 2013 study about eggs “might make you swap sunny-side up for a whites-only omelette.” We asked Beck to revisit her 2013 article on the subject and provide an up-to-date explanation of eggs’ bad rap – and current dietary recommendations:

A 2013 report, published online in the American Journal of Clinical Nutrition, concluded that eating an egg a day – yolk included – did not increase the risk of cardiovascular disease in healthy people.

The bad news: Egg eaters were more likely to develop type 2 diabetes. And among people who already had diabetes, an egg-a-day habit substantially upped the likelihood of a heart attack or stroke. That said: Cholesterol is essential for life. It’s needed to build cell membranes, form healthy nerve fibers and make vitamin D and hormones such as estrogen and testosterone.

Although high blood cholesterol is an established risk factor for a heart attack and stroke, the link between cholesterol in foods and cardiovascular disease remains unclear. Most studies have found that dietary cholesterol has little, if any, impact on blood-cholesterol levels.

While eggs may have little effect on your fasting blood-cholesterol level, that may not be the case for your “after-meal”, or postprandial, blood cholesterol. (Fasting blood cholesterol is measured after consuming no food or drinks, with the exception of water, for nine to 12 hours.)

There is mounting evidence that, depending on what you eat, postprandial blood fats can damage blood vessels and promote atherosclerosis (hardening and narrowing of the arteries). Small studies have shown that eating a cholesterol-rich meal can enhance the blood-cholesterol-raising effects of saturated (animal) fat and increase the chance that your LDL (bad) blood cholesterol becomes oxidized.

So what are we to make of all this? Are eggs off the menu? Most people don’t have to worry about eating an egg yolk to two each day; the evidence that the amount of cholesterol you eat raises LDL blood cholesterol is weak.

So weak, in fact, that scientific advisory panel for the 2015 iteration of the Dietary Guidelines for Americans is recommending the decades-long recommendation to avoid eating foods high in cholesterol be dropped.

Some people, though, are sensitive to the blood cholesterol-raising effect of food cholesterol. People with diabetes and those with heart disease should limit their intake of egg yolks to four per week (some experts advise avoidance).

Instead of eating a two-egg omelette with 266 milligrams of cholesterol, have a cholesterol-free white-only omelette for a good source of protein, riboflavin (a B vitamin) and selenium. Try a cholesterol-free egg product sold in the egg case at grocery stores.

Keep in mind that there are variables we do not yet know. It’s possible that consuming antioxidant-rich foods (e.g. berries, citrus fruit, red peppers, spinach, green tea) or anti-inflammatory foods (e.g. salmon, chia seeds, ground flax, walnuts) with an egg could mitigate the harmful postprandial blood fat effects.

But most of all, let’s not forget that preventing cardiovascular disease is about a whole lot more that cutting back on egg yolks. Limiting refined (white) starchy foods and added sugars, reducing trans fats, emphasizing monounsaturated fats (e.g. olive oil, avocado, almonds), increasing omega-3 fats from fish oil, limiting sodium intake, getting regular exercise and maintaining a healthy weight are key strategies to guard against heart disease and stroke.

Follow Leslie Beck on Twitter and read more of her columns here

Are nutritional supplements a beneficial addition to retaining muscle?

Reader Sandra in Vancouver. asks: “Are nutritional supplements a beneficial addition to gaining, maintaining and retaining muscle for an active 56-year-old woman? I eat well and exercise, but have a tough time keeping muscle.”  Globe Health’s fitness expert Kathleen Trotter explains:

First, let me say that having blood work done is the only way to learn with any certainty what vitamins and electrolytes you are deficient in, and therefore what supplements you actually need. If you think you are not gaining muscle or are recovering poorly because you are deficient in a particular nutrient, you may want to ask your doctor to run some key blood tests or consult a naturopath, who can facilitate a set of tests.

But before you invest time and money on blood work and supplements (they can get expensive), I suggest you analyze your diet and exercise routine. I know you say you “eat well and exercise,” but it is possible that your regimes, although beneficial to your overall health, are not geared to increasing muscle mass.

I am curious how you define eating well. In my experience, some people think a healthy diet means simply restricting calories and fat. You might not be eating enough protein, overall calories or healthy fats to gain muscle. You might not need supplements – you might just need to tweak your diet.

My next question: what’s involved in your exercise program? Some women prioritize cardio and core work over strength training, and when they do lift weights, they do endurance-based strength training. This means they use a light weights to do two or three sets of 12 to 15 reps of each exercise. For a hypertrophic response (i.e to increase muscle size) you need to do three to five sets of eight to 12 reps of each exercise with a heavy weight.

If you do decide to take supplements, I recommend talking with a knowledgeable health professional, or at a minimum researching the recommended doses of any supplement you are contemplating taking.

Consuming excess vitamins can be toxic. As a general rule, water soluble vitamins are safer because excess will be excreted. That said, every rule has an exception. Excess vitamin C – a water soluble vitamin – can contribute to kidney stones. Excess of fat soluble vitamins – A, D, E and K – will be stored in your liver and body fat, and therefore are potentially more harmful.

You can consume the absolute perfect combination of nutrients – either through food and/or supplementation – but if your body is not digesting or absorbing them you won’t get the full benefits. A quality probiotic can aid in digestion. Consider asking your health professional about whether you could benefit from a probiotic. Or experiment with foods such as kefir and kimchi.

Remember: Be cautious. Research the recommended doses and contraindications of anything you are contemplating taking.

Follow Kathleen Trotter on Twitter and watch her Fitness Basics videos.

Which foods and drinks add to fat in the mid-section?

Reader Ann Ranson in Ottawa asks, “Which foods and drinks add to fat in the mid-section?” Globe Health’s fitness expert Kathleen Trotter says, “Great question. Excess abdominal fat can be aesthetically annoying, but it is also associated with a higher risk of developing diabetes, heart disease, high blood pressure and high cholesterol.

Food and drink wise, my recommendation is simple: Avoid fried, processed and sugary foods. Instead, eat nutritionally dense, non-processed high fiber foods such as nuts, legumes, fruits and vegetables. Drink water, not sugary juice. Also, make daily movement a priority. I know  – what surprising suggestions coming from a personal trainer!

My slightly more nuanced answer is that stress levels are a big part of the battle against tummy fat. There are many interconnected variables that influence where fat will get deposited: your metabolism, your hormones, how well your body metabolizes glucose, your activity level, your diet, and – this is the big one – the amount of stress you are under.  (My favorite way to de-stress is to get a massage. If I ever win the lottery I will get one daily.)

Prolonged periods of stress – especially when the stressor is perceived as insurmountable – create a cascade of hormonal reactions that result in the release of cortisol.  Under healthy, non-stressed cicumstances, cortisol is a necessary hormone –  but under high stress, it will tell your body to deposit fat around your tummy.

So if you and a friend both eat a cookie, and you are stressed and she is serene, your cookie is more likely to be stored as fat around your mid-section.

The good news: exercise can help. Here’s how:

Mindfulness Training: Experiment with mindful exercise programs such as yoga, Tai Chi or meditation that can help manage stress.

Interval Training: Two or three times per week, do cardio intervals. Interval training improves cardiovascular fitness, insulin sensitivity, HDL (the good) cholesterol and helps to reduce both visceral and subcutaneous fat. For some fun interval workouts take a look here and here.

Resistance Training: This can help to maintain or increase your lean muscle mass, decrease your overall body fat and improve your metabolism. Prioritize multi-joint full body exercises like squats, push-ups and pull-ups, and core exercises such as planks.

Check out these specific resistance exercises to strengthen the muscles around your torso,  but keep in mind that no amount of crunches is going to decrease tummy fat. The only ways to do that are to decrease stress levels and reduce overall body fat levels with diet and exercise.

Follow Kathleen Trotter on Twitter and watch her Fitness Basics videos.

When will the law change to decriminalize doctor-assisted deaths?

Andrew Lemeuw in Toronto asks: “When will the law change with the new decriminalization of doctor-assisted deaths?  The Globe’s justice reporter Sean Fine, who covered the historic Supreme Court ruling, has the answer:

No later than Feb. 6, 2016.

The Supreme Court of Canada gave the government of Canada one year to draft new laws, if it wishes, to govern physician-assisted death. In a legal sense, Parliament could just do nothing; politically, though, that is highly unlikely, as the Conservative government would be seen as abdicating its duty to Canadians.

If Parliament approves no new law on assisted death by next February 6th, the law would change on that date to permit assisted dying for some suffering adults. This is a very serious right — control over one’s life covering what the court called “the passage into the death.” It can’t be held back by government inaction. Government can’t limit this right more than the court will allow.

The government has not publicly said whether it will introduce and try to pass a new law before the election. “This is a sensitive issue for many Canadians, with deeply held beliefs on both sides,” Clarissa Lamb, a spokeswoman for the federal Justice Department, said in an email. “We will thoroughly and thoughtfully study the Supreme Court’s decision . . . and ensure all perspectives on this difficult issue are heard. We will consult widely with Canadians and review the decision comprehensively before deciding how to respond.”

The Supreme Court set the parameters for any new law on physician-assisted death for ill people, and they are wide. They do not just cover the terminally ill. And “intolerable” suffering needs to be seen through the eyes of the ill individual. This group includes those who are suffering psychologically. The court said that the assisted-suicide laws currently on the books will not be considered valid “to the extent that they prohibit physician-assisted death for a competent adult person who (1) clearly consents to the termination of life and (2) has a grievous and irremediable medical condition (including an illness, disease or disability) that causes enduring suffering that is intolerable to the individual in the circumstances of his or her condition.”

Provincial governments, too, may wish to draft laws on assisted dying, since health care is a shared responsibility with Ottawa. Quebec already has drafted one such law, which was almost certain to be found unconstitutional if the court had upheld the Criminal Code provisions on assisted suicide; the constitution bars provinces from legislating in areas covered by the criminal law, which is exclusively federal jurisdiction. As it is, the Quebec law on assisted death would likely run afoul of the Supreme Court ruling, in that it applies only to the terminally ill.

The February 6, 2016 deadline poses a challenge for the federal government, as summer recess is coming and an election is expected next October. Some had suggested the Justice Department would ask the court for an extension, but that seems highly unlikely, and it is not difficult to imagine how the court would treat such a request.

Follow Sean Fine on Twitter , read the Globe’s editorial on the Supreme Court decision, and the Globe Debate column:  Next step in assisted suicide: Ensuring it can be done humanely


I have been vaccinated for measles. Am I protected against new strains that have infected 11 people in Ontario?

Reader Sarah Polk in Montreal writes,”Does the immunity that Canadians currently have due to measles mumps and rubella (MMR) vaccination protect us against new strains that have infected 11 people in Ontario?” The Globe’s public health reporter André Picard says, “The short answer is yes.” While there are various strains of the measles, Picard says the vaccine protects against all strains. “That means the MMR (measles-mumps-rubella) shots children receive provide life-long immunity, with few exceptions.” Picard explains:

The confusion arises because the flu shot is required every year. That’s because flu viruses mutate and the strains that circulate can change markedly from year-to-year.

With measles, there are different strains, but very little variation between them, so the immune system recognizes them all as measles – if you have been properly vaccinated, or if you had the measles, and developed immunity.

People born before 1970 likely had measles and don’t need to be vaccinated. Those born between 1970 and 1979 probably had only one measles shot and likely need a booster. People born between 1979 and 1996 may or may not have had two MMR shots, depending on where they live. In some cases they may need a measles booster (or, more likely, a mumps booster). A two-dose MMR vaccine has been standard since 1996.

If you are unsure of your status, the easiest thing to do is get another shot. That is especially important if you are travelling to areas of the world with a lot of circulating measles, like India, the Philippines or France.

So why does it matter if there are new strains circulating?

Molecular genotyping of the type that identified the unusual strain in Toronto is done to facilitate global surveillance and outbreak investigations. If you know where the strain originated it’s easier to trace how people got infected and contain the spread.

For example, researchers know that an outbreak of 141 cases that has spread to 17 U.S. states (and Quebec) all originated at Disneyland, and that the strain is similar to strain that fuelled a large outbreak in the Philippines. The Ontario cases, on the other hand, have a different genetic fingerprint and the source has yet to be identified.

Since 1990, 19 different strains have been catalogued and sequenced: A, B2, B3, C1, C2, D2, D3, D4, D5, D6, D7, D8, D9, D10, D11, G2, G3, H1, H2. The Disneyland cases are a B3 strain.

A global measles sequence database, MeaNS, has been established at the Health Protection Agency in London, and contains sequence information from more than 10,000 measles samples.

Follow Picard on Twitter, and read The misery of measles in a world without vaccines