Influenzas with zoonotic potential: the contribution of the animal health sector for pandemic preparedness

It is winter, you feel tired, you have a headache, muscle aches and a sore throat. You know flu season is ongoing. Every year, usually during the fall and winter, millions of people around the world get sick with the flu, short for influenza. Today, vaccination represents one of the most well-known means to protect humans against the viruses that are each year responsible for hundreds of thousands of seasonal flu infections. Flu viruses, including those in animals, continuously evolve and vaccines may become inefficient against them. To remain effective, new vaccines need to be developed periodically. Every six months, the composition of the human vaccines against flu is reevaluated, based on data collected through the surveillance of virus strains circulating in humans, but also in animals, in particular for the strains that can become zoonotic.

Stemming the spread of seasonal flu with vaccination

Responsible for around 5 million cases of serious illness, and 290,000 to 650,000 global human deaths annually, seasonal flu continues to be a major public health concern. These annual epidemics are fueled by the flu viruses’ ability to continuously evolve. Their properties can change, the viruses can become more transmissible and current vaccines against them may be less effective.

Since the 1940s, 80 years ago, medical research has made available an effective measure to fight the flu: an annual vaccine. Vaccination remains a top recommendation from the World Health Organization (WHO), especially for people who are most at risk, and there are many reasons as to why. First off, receiving a flu shot keeps numerous people from getting influenza symptoms, and for those who still get sick, they usually experience less severe illness.  As an example, in the United States of America, during the 2019-2020 period, flu vaccination prevented an estimated 7.5 million flu cases. But perhaps the most important reason of all is that getting vaccinated helps mitigate the spread of the disease, by obtaining population immunity.

Twice a year, the World Organisation for Animal Health (OIE) and its partners contribute to the surveillance of flu viruses in animals including those that have pandemic potential for humans, by collecting and analysing data on these viruses, such as avian influenza. We help ensure that, should these viruses with zoonotic potential make the jump from animals to humans, leading to a pandemic, the appropriate vaccine is rapidly developed with the best protection possible.

Considering avian influenza viruses to develop human vaccines

Effective vaccination requires that both human and animal sectors conduct significant surveillance and be on the lookout for animal viruses with zoonotic potential, which could possibly not match the strains used in current flu vaccines. When such viruses are found, it is paramount that they are considered to make pre-pandemic vaccines. In this regard, the WHO shares biannual recommendations on the updated composition of flu vaccines, taking into account OIE’s knowledge on the circulation of animal influenza viruses.

Animal influenzas, such as avian influenza, share genetic similarities with the human flu viruses. Because of their potential to evolve genetically and be passed to humans, avian influenza viruses are considered a public health concern. Avian influenza, commonly known as bird flu, and human influenza are linked within a complex system. Their constant evolution calls for significant surveillance to gather the necessary data to develop the vaccines. Setting international standards on surveillance, the OIE works with global partners like WHO and the Food and Agriculture Organization of the United Nations (FAO) as well as its Reference Laboratories to collect scientific information on animal flu viruses. The OIE also encourages countries to report outbreaks of avian influenza and share their data through its World Animal Health Information System (WAHIS).

When the animal health sector takes the lead

In the process of developing human vaccines, veterinary expertise is key. As a part of its long-standing mandate, the OIE ensures the dissemination of animal health scientific information. This data is collected through WAHIS and supplemented with genetic and antigenic data by OIE Reference laboratories and national animal health laboratories in countries all over the world. This international contribution allows crucial information from the animal health sector to be used by WHO to determine and update their recommendations for human vaccines against flu viruses of concern.

Moreover, since 2005, the joint OIE-FAO scientific network on animal influenza (OFFLU) works bilaterally with Reference and national laboratories experts worldwide to encourage the publication of data related to animal influenza strains on publicly accessible databases. Undeniably, to analyse and exchange scientific data on animal influenzas with the wider scientific community is crucial to update the vaccines and adapt them to circulating field viruses.

And the veterinary work does not stop there. Annually, the OFFLU network provides the WHO Global Influenza Surveillance and Response System (GISRS) -those in charge of recommending the strains to use in human flu vaccines- with molecular and epidemiological data to support the selection of the next vaccine’s composition to make human vaccines that could prevent a pandemic. 

How the pandemic potential of the flu calls for a One Health approach

Over the past few decades, the transmission of flu viruses across different species has been observed. Notably, humans have been infected with bird flu on a number of occasions, including the episode of global concern in 2005/2006 when the subtype H5N1 had a peak of spread to humans. Even if the risk of bird flu transmission to humans remains low, these sporadic zoonotic infections remind us that the threat of an influenza pandemic persists. In this COVID-19 era, we cannot let our guard drop, and must work towards international collaboration on disease control and response, across sectors. To best prepare against a future pandemic, the world must adopt a One Health approach, that considers human health, animal health and environmental health as interdependent.

3 facts about influenzas
Flu is short for influenza
The first known influenza pandemic struck in 1580
The first vaccine against the flu was developed 80 years ago, in the 1940s