Science·What on Earth?

Infectious diseases and climate change: Is there a connection?

In this week's issue of our environment newsletter, we look at climate change and the spread of infectious diseases, the phantom power of your electronic devices and the possibility of a plastic-free period.

Also: A primer on reusable menstrual products

(Sködt McNalty/CBC)

Hello, people! This is our weekly newsletter on all things environmental, where we highlight trends and solutions that are moving us to a more sustainable world. (Sign up here to get it in your inbox every Thursday.)

This week:

  • What's the connection between climate change and infectious diseases?
  • Your electronics are energy suckers, even when you're not using them
  • A primer on reusable, plastic-free menstrual products

What's the connection between climate change and infectious diseases?

(Hector Retamal/Getty Images)

We still don't know where the 2019 novel coronavirus came from. The leading suspicion is an animal host – a bat, likely – infected another animal that has more contact with humans. 

That's how the 2012 MERS (Middle East Respiratory Syndrome) outbreak is believed to have played out. A bat, at some point in the past, infected a camel, which may have sneezed on a human. 

One of the reasons the human and animal worlds are bumping up against each other is a changing climate. Research suggests that warmer winters and springs are keeping bats, for example, around longer because the insects they feed on also like the warmth. And this may affect the spread of diseases bats carry.

"Climate change, coupled with other human environmental changes like urbanization and habitat destruction, is bringing us closer to wildlife," said Dr. Katie Clow, a professor at the Ontario Veterinary College at the University of Guelph. "So there's this very complex interplay of many different changes happening all at the same time."

Clow's research looks at the epidemiology of vector-borne diseases and a lot of her work involves trawling the woods for ticks. (She also has the pleasure of getting those little buggers in the mail.) The study of ticks provides some of the clearest evidence of the effect of a warming climate on the spread of infectious diseases.

Take the blacklegged tick, for example. 

"We know that climate change has had a huge influence on allowing it to expand its range into more temperate areas," Clow said. "The warm period of our summers and springs lasts longer than it used to. And [the blacklegged tick's] reproduction and ability to sustain that reproduction is based on having a climate that's warm enough, for long enough."

This is dangerous because ticks can carry Lyme disease, which can cause rashes, joint pain and even serious neurological issues in humans and pets. 

But this seemingly straightforward cause and effect hides complexity. Expanding the range and lifecycle of a tick is one part of a climate equation that may well involve humans spending more time outdoors because of those same warm temperatures. That complexity makes it hard to determine climate change's effect on other pathogens, like the novel coronavirus or influenza. 

"Generally, influenza viruses survive better when it's cooler, especially in the tropics," said Dr. Nicholas Ogden, a veterinary epidemiologist at the Public Health Agency of Canada. "Of course, in winter, people [also] tend to be congregated together. So there are some seasonal aspects that are difficult to tease apart." 

In essence, one environmental factor may contribute to the decrease of a specific pathogen while another may keep it alive. This complicates the search for clear cause and effect, and shows why other forecasted disease risks of climate change demand further research. 

Here are some other potential risks that scientists have highlighted: 

  • Severe flooding and heavy rainfall events may lead to water-borne illnesses such as cholera and leptospirosis.

  • Hotter temperatures can cause food-borne illnesses from a higher risk of food spoiling.

  • Human migration (because of climate, economic and sociopolitical factors) can cause non-native pathogens to be carried to new places in big numbers.

Scientists say there is a connection between climate change and the spread of disease, and figuring it out is the only way to develop better public health strategies. 

"There is increasing evidence that climate change is having an impact on health," Ogden said, adding that disease is "part of the impact that we need to identify, predict and be prepared to adapt to." 

Anand Ram

Reader feedback

Last week, we published a story on microgrids in which we cited one built in Sendai, Japan, a decade ago as an "older" example. This prompted reader Mitch Wright to point out that the concept has existed for quite a while. "Many small towns in Ontario that were built on rivers installed their generation plants long before the towns were connected to an Ontario grid. This is because the grid did not exist yet. In Wingham, Ont., where I currently live, [power] generation was installed between 1900 and 1910 and ran for 20 to 30 years before the Ontario grid was extended to Wingham."

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Old issues of What on Earth? are right here.

The Big Picture: The phantom power of your electronics

Many of our modern devices are reliant on electricity, and a lot of us are quite content to leave them plugged in all day long. But these appliances draw electricity even when they're not in use — so-called phantom power. According to the Ontario utility Hydro One, the average Canadian home contains more than 20 devices that draw phantom or "standby" power, which can account for up to 10 per cent of home energy use. Fixing the problem is as simple (or complicated) as unplugging every appliance you own when it's not in use or deploying advanced power bars that can time out or sense when devices are idle. Here's a look at the energy use of some typical electronic devices.


Hot and bothered: Provocative ideas from around the web

Plastic-free periods: Reusable menstrual products are going mainstream


Every year, tens of billions of single-use pads and tampons go into landfills — material that takes hundreds of years to decompose. The average user goes through between 5,000 and 15,000 pads and/or tampons in a lifetime. 

Amanda Laird, author of Heavy Flow: Breaking the Curse of Menstruation, believes our society's reliance on disposable menstrual products began in the 1920s. "As a way to market the products, [advertisers] had to position periods as something that was dirty, gross and unsanitary," she said.

Reusable menstrual products have been around for a while, but they're becoming increasingly mainstream. Dr. Yolanda Kirkham, a gynecologist at Women's College Hospital and Unity Health Toronto, said a lot of her patients have been using reusable products for several years, indicating those who make the switch end up sticking with it. 

The main players on the reusable market right now are menstrual cups and period panties or pads. 

Menstrual cups (to the left in the photo above) are bell-shaped and typically made of silicon or latex rubber. To insert, users fold them tightly and push them through the vaginal canal like a tampon without an applicator. There are different sizes, depending on factors like flow and whether or not the user has given birth. Once released, the cup springs out to suction against the cervix, resting on the vaginal walls to catch fluid.

The other option is period panties or pads, made with layers of absorbent, moisture-wicking materials like organic cotton and polyester. Some choose to use them as a backup for cups or tampons, while others use them solo. 

For cup care, Kirkham recommends rinsing it out every four to six hours, boiling it between cycles and replacing it if there's damage. Manufacturers recommend replacing it every one to two years, but it can be used for up to 10 years, according to a 2019 study on menstrual cup safety. 

External reusables like pads and panties should be rinsed and washed in warm water between use, said Kirkham. Most companies say to hang dry. 

One rare risk associated with period products is toxic shock syndrome, a severe bacterial infection that can cause dizziness or faintness, vomiting, diarrhea and a rash on the palms, said Kirkham. 

Infections can happen "any time there is a break in the barrier to our body system," she said. "So anytime there's a bit of friction, there's a possibility for a micro tear and that's how bacteria can get in." 

There's no consensus among users about whether reusables or disposables are healthier. Some argue reusables are less hygienic, while others believe the chemicals in tampons and pads are harmful.

Menstrual cups and washable pads are "just as safe" as disposable products, while the latter contain smaller amounts of chemicals than many foods, said Kirkham. She advises avoiding products that aren't well-recognized or medically regulated, such as crochet tampons and sea sponges, which are often marketed as natural and eco-friendly options. 

While Laird believes reusable products are a great option for the environment, "we have to recognize that they aren't right for everybody."

"Not everybody can get up close and personal with their menstrual blood," she said.

Isabel Terrell

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Editor: Andre Mayer | Logo design: Sködt McNalty


  • A previous version of this story referred to ticks as insects. They are in fact arachnids.
    Feb 11, 2020 3:42 PM ET


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