How do scientists predict the influenza that will be here each year?

Influenza virus prediction is a complex process that involves multiple steps and collaboration among scientists from different fields, including virologists, epidemiologists, and molecular biologists. Here are the key steps involved in predicting the influenza strains that may circulate each year:

1. Global Influenza Surveillance:

- Influenza viruses are constantly evolving and circulating worldwide, so scientists maintain a year-round surveillance system to monitor influenza activity and identify emerging strains.

- This involves collecting respiratory samples from individuals with influenza-like illness, isolating the viruses, and conducting laboratory tests to characterize them.

- The World Health Organization (WHO) coordinates this global surveillance network and regularly updates the information on circulating influenza strains.

2. Antigenic Analysis:

- Scientists analyze the antigenic properties of influenza viruses to predict which strains may be most likely to cause the next seasonal flu.

- They focus on the two surface proteins of the virus: hemagglutinin (HA) and neuraminidase (NA).

- These proteins are responsible for the virus's ability to infect cells and cause disease, and changes in their structure (antigenic drift) can result in new strains that the human population lacks immunity to.

3. Phylogenetic Analysis:

- Scientists use phylogenetic analysis to assess the genetic relatedness of circulating influenza viruses.

- By constructing phylogenetic trees, they can identify distinct genetic lineages and track their evolution over time.

- Genetic changes that indicate a significant divergence from previous strains are important in predicting the emergence of new pandemic or epidemic influenza strains.

4. Animal Studies:

- Animal models, such as ferrets and mice, are used to study the pathogenicity and transmissibility of different influenza virus strains.

- Scientists can evaluate the severity of disease caused by candidate vaccine strains and their potential to spread within a population.

5. Expert Consultation and Risk Assessment:

- WHO convenes panels of experts, including virologists, epidemiologists, and public health specialists, to review and interpret the surveillance data, antigenic analysis, and animal study results.

- These panels assess the risks associated with various circulating strains and make recommendations on which strains to include in the annual influenza vaccine.

- The recommended vaccine strains are typically announced several months before the start of the influenza season to allow manufacturers to produce and distribute vaccines.

6. Vaccine Production:

- Based on the expert recommendations, vaccine manufacturers produce vaccines containing antigens that match the predicted influenza strains.

- Multiple influenza vaccine formulations are typically available to cover a range of potential circulating strains and provide broad protection.

It's important to note that influenza virus prediction is not an exact science, and there is always some uncertainty associated with the process. However, the scientific community's collaborative efforts and sophisticated surveillance systems have greatly improved the accuracy of influenza strain prediction, leading to more effective vaccines and better public health preparedness for seasonal influenza epidemics.