As researchers scramble to make sense of the new H1N1 influenza virus that is spreading across the globe, the Centers for Disease Control and Prevention reported encouraging signs last Sunday on the outbreak’s severity, but kept a wary stance on how the virus will behave in the future.
Although the current H1N1 strain lacks the deadly markers seen in its infamous 1918 predecessor, UC Davis researchers agree that it is still too early to make comparisons regarding the threat that it poses toward public health.
“It is not deadly thus far in comparison to other [influenza viruses] but it can evolve,” said Christian Sandrock, a physician at the UC Davis Medical Center department of pulmonary and critical care medicine.
Sandrock explained that the damage potential could grow as the virus mutates and adapts in human hosts, but cautioned that there is still plenty that researchers do not know about this process.
“A virus as it adapts to humans can become less virulent [disease causing] in order to improve transmission. This is the theory for [some strains of] H5N1 avian influenza,” he said. “However, it could remain highly contagious and virulent, and we are not sure what it was about the 1918 virus that was so deadly.“
Studies indicate that virulence is determined in part by genetic traits that influenza viruses have evolved in hosts to bind to and enter target cells in the respiratory tract, thwart immune responses and replicate by hijacking the host cell’s machinery.
“Then transmissibility from person to person is influenced by a different set of genetic changes [mutations],” said Kathryn Radke, an animal science professor at UC Davis.
The H and N in influenza classification refer to two types of surface proteins on the virus that it uses to first enter host cells and then exit after making new copies of itself for subsequent rounds of infection.
“[Mutations] in those two molecules will have a big effect on which cell types it can infect and which species it can infect,” said Nicole Baumgarth, an associate professor at UC Davis‘ Center of Comparative Medicine.
Because pigs are vulnerable to infection by bird and human influenza viruses, researchers think that four different strains from these three species have mingled and swapped pieces of their genetic material in swine to give rise to the new H1N1 virus before it jumped into humans.
CDC researchers announced that plans are under way to develop a vaccine against the new strain, but the decision to go forward with large-scale production has not yet been made.
Despite the multi-faceted challenges of curbing a pandemic, some experts agree that the scientific and medical communities are in better shape than before to detect and track the course of this influenza outbreak.
Greater surveillance and intensive planning models can indicate the best steps to take at various stages such as school closure, Sandrock said.
“However, we still are not preventing high risk animal-human and human-human interactions [by improving living conditions, nutrition and health],” he said. “As the world expands and we encroach upon wildlife, we will see interactions that increase the likelihood of [viral] transmission [into humans]. “
Carol Cardona, a veterinarian and extension specialist at the UC Davis School of Veterinary Medicine, noted that the threat remains for the much deadlier bird flu to become widespread in humans. Unlike H1N1, avian H5N1 has not yet adapted to spread efficiently from person to person.
“The world has never [before] seen two pandemic virus potentials happening at the same time,” she said. “Today, you can see all these pandemic plans going into action very quickly and that’s because we’ve prepared for bird flu. … [I think] we were prepared to find something that was not normal, and that, in and of itself, has led to a very early and effective response.“
ELAINE HSIA can be reached at email@example.com.