U.S. health officials are tracking a newly discovered strain of swine flu in China they say has the characteristics of viruses with potential to cause a human pandemic. However, the virus has not been detected in the U.S.
Researchers conducting surveillance on pigs in China found genotype 4 (G4) Eurasian avian-like H1N1 viruses have been detected since 2016, as they reported in Proceedings of the National Academy of Sciences.
The strain has genes from a mix of pig, avian and human viruses and genes from the 2009 H1N1 flu pandemic virus. Genetic material can mix in an animal host through a process called reassortment, creating a new virus, according to Flor M. Munoz, M.D., M.Sc., FAAP, a member of the AAP Committee on Infectious Diseases.
The new strain appears to grow well in human airway epithelial cells and possesses “all the essential hallmarks of being highly adapted to infect humans,” according to the study.
Testing of 338 swine workers in China found 10% had evidence of a past infection. There are no reports of person-to-person transmission, but experts say the virus may continue to adapt and mutate.
The Centers for Disease Control and Prevention (CDC) called the strain a “potential pandemic concern,” because of its novelty. Humans don’t have immunity to this new virus, and it is too different from seasonal flu vaccine strains for these vaccines to be effective. However, it has not been found in humans or pigs in the U.S.
Dr. Munoz said the findings should not be taken lightly, and notes that the identification of this new strain is a result of the effective surveillance systems that are in place through the CDC and World Health Organization (WHO) to track the emergence of new influenza virus strains.
“Whether this strain is going to become a problem for humans in the future, we don’t know now, but it is reassuring that global surveillance is in place to be prepared,” she said.
The CDC said it is coordinating with public health partners in China and studying whether existing flu antiviral drugs are effective against the new strain. It also is evaluating whether a genotype 5 candidate vaccine virus developed by the WHO could provide cross-protection. If necessary, it said it would create a new candidate vaccine virus specific for this new strain.
“We shouldn’t let our guard down with influenza because there’s always going to be a possibility of new threats from emerging strains, and hopefully we can learn from our experience with COVID to be better prepared,” Dr. Munoz said. “… This is also a reminder of why we need to be part of the global community and the WHO for sure.”
The Trump administration recently began the process of formally withdrawing from the WHO. AAP President Sara “Sally” H. Goza, M.D., FAAP, joined other medical leaders in a statement Tuesday saying the decision “puts the health of our country at grave risk.”
"As our nation and the rest of the world face a global health pandemic, a worldwide, coordinated response is more vital than ever,” they said. “This dangerous withdrawal not only impacts the global response against COVID-19, but also undermines efforts to address other major public health threats.”
