Look at those soft, brown eyes, that adorable nose, the movement-sensitive whiskers and winsome smile.
Meet the Atlantic harbor seal. This mostly marine neighbor raises its young on beaches, pleasing human onlookers with its barks and yawns and tricks.
Who would think that an illness in this population would rock New Englanders and spark scientific studies?
In the autumn of 2011, more than 160 seal pups, sleek and furry and dying, washed ashore and sounded an influenza alarm.
A mutated form of the avian virus H3N8 influenza A was the culprit. It had jumped from birds (likely waterfowl) to harbor seals.
Could it threaten us?
“The big concern was obviously whether it would infect humans,” says Infectious Diseases researcher Stacey Schultz-Cherry, PhD, a lead investigator in a St. Jude Children’s Research Hospital study that appeared in the journal Nature Communications.
Although no human illness was linked to that harbor seal virus, scientists noted that strains of H3N8 have also been detected in horses, dogs, donkeys and pigs. The virus is believed to have triggered a human flu pandemic in the 1880s.
A red flag
St. Jude scientists discovered that two mutations in the hemagglutinin protein and a change in the PB2 gene were the culprits in the recent harbor seal event.
Schultz-Cherry explains, “At St. Jude, we didn’t do anything with the seals themselves; all of our work was in the lab. When we saw that H3N8 could grow well in mammalian cells and could transmit disease, we wanted to know: If this virus came in contact with humans, would we have any protection against it?”
In short: No.
Investigators found no evidence of human immunity to this H3N8 strain and no evidence that seasonal flu vaccines would thwart it.
“Our study raises a red flag about the threat this strain poses to humans who are exposed to animals infected with the virus,” Schultz-Cherry says. “We need to do a human risk assessment study.”
Risk of infection is a major concern at St. Jude, where insight into contagious diseases is critical to treating immune-compromised cancer patients.
“Doing these studies is so important at St. Jude, because we have a susceptible population,” Schultz-Cherry explains.
St. Jude influenza research began in the 1970s with work spearheaded by internationally renowned scientist Robert Webster, PhD, who now holds the Rose Marie Thomas Chair in Infectious Diseases. As a result of Webster’s work, the scientific community learned that aquatic birds are the reservoir for influenza A viruses.
Since 1975, St. Jude has been a World Health Organization (WHO) Collaborating Center for Studies on the Ecology of Influenza in Animals and Birds. Today, St. Jude remains on the forefront of flu research.
“We help decide which influenza strains are going to be in the vaccines,” says Schultz-Cherry, deputy director of the St. Jude WHO center, “and St. Jude helps make vaccine seed stock for the pandemic viruses.”
St. Jude is also one of five U.S. research institutions designated as a Center of Excellence for Influenza Research and Surveillance by the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health.
So, when the complexity of the New England harbor seal deaths emerged, St. Jude was asked to assist.
Originally, the event involved investigation of five harbor seals, mostly pups that were in generally good physical condition, not malnourished. After avian H3N8 influenza A was confirmed, state and federal officials collected more samples from harbor seals stranded in Maine, New Hampshire and Massachusetts.
In the St. Jude study, scientists found that H3N8 naturally acquired genetic changes.
“Either by going into the seals or by going seal to seal, that virus mutated,” Schultz-Cherry explains. “And the virus is really sloppy. When it grows, it can’t fix any mistakes—kind of like turning off spell-check. It just types away, makes mistakes and has no way to backspace and delete. Sometimes you see changes that make a virus better suited for a new mammal, or that make it grow more effectively to be able to transmit.”
At St. Jude, Schultz-Cherry and her colleagues look at those genetic changes and spot concerns that might indicate a need to produce new antivirals or vaccines.
“We want to know if these new influenza strains come from animals or birds, if they are going to create a public health problem and if so, how serious would that problem be? Would it affect everybody, or just pose a risk to people who have compromised immune systems, such as our St. Jude patients? We do risk assessment studies: What is the risk to the public? Do we have therapies or vaccines or antivirals that are going to work against these infections?
“You couldn’t do work like this any place else. That’s why I came here—to move this work forward from the laboratory to the bigger area of public health for children.”
So how does this unique H3N8 move from harbor seals to other mammals?
Scientists learned that the virus is transmitted through respiratory droplets.
Would that imply sneezing seals?
“Absolutely right!” Schultz-Cherry says. “How do you get influenza but through aerosols—coughing, sneezing?
“People shouldn’t be afraid of seals,” Schultz-Cherry continues, with a laugh. “Still, I wouldn’t run up and kiss one.”
Abridged from Promise, Winter 2015