Sled Dogs, Serum, and Hidden Stories behind the Iditarod
By Molly Cavanaugh, March 2026
The story usually associated with the Iditarod is one of bravery, a deadly disease, and the mushers who saved the day. In 1925, Nome was stuck in a worsening diphtheria epidemic (1). Diphtheria is a bacterial disease (with a secret weapon discussed later) which causes a fever, a thick gray coat on the throat and tonsils, difficulty breathing (and can even prevent breathing), and extremely swollen glands in the neck (2). The infection is deadly in 5-10% of cases, with the toxin produced by diphtheria causing damage to the heart and nervous system (3). Concerningly, the death rate rises to up to 30% in children under 5 (4). In 1925, Nome had a single doctor: Dr. Curtis Welch. Dr. Welch begged the territory of Alaska to step in and to send anti-serum to the town of 10,000 (5).
The sea around Nome was frozen, rendering ships useless. The weather was beyond dangerous with blizzard conditions making approaching by plane impossible. There were also no roads leading to Nome at the time. This left one option; the serum would be taken from the port of Seward 433 miles north by train to Nenana and then sled dog teams would take the serum the remaining 674 miles. The brave men and dogs of this expedition included Leonhard Seppala, a champion musher, with his lead husky Togo, and Gunnar Kaasen, with his young lead dog: Balto. These men and animals, along with many others, relayed the serum across 674 miles in 5.5 days, a route that typically took the US mail 30 days (6, 5).
Interestingly, the first race in 1967 organized by Joe Redington was not to commemorate the 1925 Nome Serum Run, but to save sled dog culture and preserve the Iditarod trail (7). It was not until 1973 that Redington created the first long distance sled-dog race across Alaska, the Iditarod. Since the first year, this 1000-mile race across Alaska has brought international attention to mushing and has succeeded in preserving the Iditarod trail. The Last Great Race still calls to new mushers around the world who yearn to find their place in the wilds of Alaska.
Hunter Keefe is a musher who competed in the 2023 and 2024 Iditarod races, only missing 2025 with a broken foot. He will not race this year as he is starting his own kennel and due to focusing on raising his young dogs but plans to return soon. I have known Hunter since we were in elementary school, when he announced to me that he was going to be a musher. 20 years later, he now has the experience to talk about the race, whereas I have the experience to explain the deadly disease associated with it.
Recently I asked Hunter about his experience with the Iditarod:
How did you learn about the Iditarod?
“My earliest memories of dog mushing are from watching the Balto cartoon in kindergarten after-care. This interest in the sport prompted my first-grade teacher Mrs. King into giving me reading material about the Iditarod. Which lead to me starting to follow the race on my own online.”
This is also when I learned about the Iditarod from Hunter. His passion was immediately clear, even at 6.
What is the best part of the race for you?
“The best part for me is the feeling that the race itself is the great celebration of all the work we put into getting there. After months, and many times years of stress and work, getting out on the trail is a great relief. To finally be out on the trail when it’s just me and my dogs, with all our food and equipment laid out in front of us on the trail. It almost can feel like a vacation when everything is going right. Those moments of bliss on the trail are what keep me working towards getting out there again after it’s over.”
How do you think the original race to save Nome influences the current day race?
“I think people know of the serum run story more often than the actual reasoning behind Joe Redington starting the Iditarod, which was to save the Alaskan husky. I think the story is still valuable in teaching about mushing history, inspiring the next generation, and reminding people of the sled dog’s impact on our State.”
Like Hunter, my path was set when one of our teachers gave me a book. In 7th grade, Ms. Wild gave me The Hot Zone by Richard Preston. This book, about the first Ebola outbreak, led me to become a virologist. Just as people only know part of the story of the Iditarod, there is another hidden story here. As a virologist, the 1925 Nome Serum Run intrigues me because of the disease.
Diphtheria is a deadly, but fascinating disease because the bacteria that causes diphtheria, Corynebacterium diphtheriae, cannot cause diphtheria by itself (9). Bacteria, just like humans and plants and all living things, can get viruses. The viruses that infect bacteria are called phages. The phage that infects Corynebacterium diphtheriae is the corynebacteriophage. When this phage infects this type of bacteria, the virus transfers a gene to the bacteria (10). This gene, which is not normally part of the bacteria, encodes a toxin. Now, when the bacteria infects humans, it produces a deadly toxin. This toxin is what makes diphtheria deadly because it stops the human cells from making any new proteins (11). Without the ability to make new proteins, like those required to fight the bacteria, the human cells die.
In most cases, the bacteria enters the nose and throat and then infects cells in the pharynx, the area between the nasal cavity and the throat (12). Once the bacteria infect the human cells, the toxin is produced, which then starts killing all the cells around it. All this dead tissue leads to the thick gray coat which covers throat and tonsil, a classic sign of diphtheria. This can lead to difficulty breathing and even death. But the bacteria can also enter the bloodstream, which is never good news. Once in the blood, the toxin can either attack the heart or the nerves. If the toxin causes inflammation of the heart muscle, the death rate can jump up to 50-75% (13). Another risk is to the nervous system. One study found that 15% of diphtheria cases end with nerve damage. This damage can include temporary paralysis of parts of the throat, face, and limbs, ridged or floppy muscles, and trouble moving (14). Today, there is a vaccine which is over 95% effective at preventing the disease (15). This is a miracle that could not have been imagined back in the 1925 Nome Serum Run.
The story of the Nome Serum Run, and the Iditarod are forever linked, even if Redington’s original vision had nothing to do with the Nome Serum Run. New mushers, like Hunter, have been inspired by the story of Balto and Togo for generations. Just as the race is linked with history, so too is the diphtheria bacteria always linked to the virus which makes it deadly.