The Impact Of Seasonal Influenza On Global Public Health
Sugyan K.1, Das S.2*, Bedamatta S.S.3, Sethy S.S.2, Senapati A.4
- of Veterinary Pathology, Indian Veterinary Research Institute, Bareilly-243122
- of Animal Breeding & Genetics, Indian Veterinary Research Institute, Bareilly-243122
- of Livestock Production & Management, Indian Veterinary Research Institute, Bareilly-243122
- of Veterinary Physiology & Climatology, Indian Veterinary Research Institute, Bareilly-243122
*Corresponding Author E- mail: shivanidas093120@gmail.com
Abstract:
Seasonal influenza poses a huge threat to global public health, with its impact extending beyond humans to include animal species. While we give more importance to human health, the transmission of influenza between animals and humans contributes greatly to the emergence of new viral variants with devastating consequences. This comprehensive overview explores the effect of seasonal influenza on global health through the lens of veterinary science, emphasizing the role of animals in the dynamics of influenza transmission. The intersection of human and animal health, most importantly, the role of livestock, poultry, and wildlife, in the mutation and spread of influenza viruses is analyzed. Furthermore, the article creates awareness about the challenges faced by veterinarians in monitoring and controlling influenza outbreaks in animals, which are critical in alleviating risks to both animal and human populations. The worldwide response to influenza, including surveillance, vaccination strategies and the collaboration between veterinary and human health sectors, is discussed. This article highlights the importance of an integrated One Health approach in managing the seasonal influenza threat and protecting public health worldwide.
Keywords: Seasonal Influenza, Viral Mutation, Animal-Human Interface, Influenza Surveillance, One Health Approach
Introduction:
Influenza, commonly known as the flu, is an significant health challenge that greatly affects human populations worldwide. While much importance is given to the effects of seasonal influenza on human health, studying its impact on animals is equally important. This collaboration between human and animal health forms the basis for the One Health Approach, which highlights the link between environment, humans and animals in controlling and preventing diseases. The 2009 H1N1 pandemic is a prominent example of a zoonotic influenza strain that emerged from pigs and led to a global human outbreak, significantly underlining the importance of animals in influenza transmission. Mainly, birds and pigs act as reservoirs and transmitters for influenza viruses. Pigs can harbor influenza viruses that infect humans, contributing to the emergence of new strains. Monitoring & Surveillance of Animal Health is another important aspect of controlling Influenza transmission. Veterinarians work closely with farmers, wildlife specialists and public health officials and can better identify potential disease outbreaks in animals before they spread to humans and result in pandemics. Veterinary professionals contribute to this approach by monitoring influenza in animals and helping to implement vaccination programs. These sustained efforts help mitigate the chance of influenza transmission from animals to humans, thus protecting global public health.
Transmission & Seasonal Pattern:
Transmission of Influenza viruses in animals can take various routes like direct contact, aerosols, contaminated surfaces and environmental factors. The transmission pathways vary between species but follow general patterns. Direct Transmission occurs through close contact between infected and healthy animals. This is commonly seen in poultry farms, pig farms, horse stables and kennels. Infected animals shed the virus through secretions and excretions which infect others in crowded conditions. Airborne transmission through aerosols occurs via droplets from sneezing, coughing, or breathing and generally involves the pulmonary system. Example may include swine influenza spreading in pig farms. The Fecal-Oral Transmission occurs particularly in wild and domestic birds through water sources contaminated with bird feces whereas indirect transmission is through fomites and environmental contamination. The virus can survive on surfaces like feed, farm equipment’s, clothing and animal transport vehicles. Poultry farm visitors unintentionally carry the virus from infected farms to uninfected ones if there are any weak bio-security measures. Zoonotic transmission is mostly seen in persons closely associated with the animals like the veterinarians and farmworkers. Some animal influenza strains can infect humans (e.g., H5N1, H7N9 from birds and H1N1 from pigs).
The seasonal pattern of occurrence of influenza in animals depends on climatic conditions, migration patterns and farming practices. Avian Influenza in birds is seen at its peak in the late autumn to early spring as wild birds migrating between continents during winter spread the virus along their pathways. Cold weather also enhances virus stability in the environment.The temperate regions (Europe, North America, Asia) see more outbreaks in the winter whereas tropical regions have sporadic cases year-round in the bird markets; indicating the geographical variations.
Likewise, the Swine Influenza virus has its peak season in late autumn to winter which is much similar to human flu prevalence for the same reason of virus stability in the cold environment. Increased indoor confinement of pigs in winter increases the intra-sty transmission. In temperate regions, cases spike in colder months. In warmer regions, sporadic outbreaks are seen throughout the year. Equine Influenza has peak season in the late winter to spring with the reason being the major horse racing and equestrian events occuring in spring which increases the speed of transmission through contact. Cold, dry air also facilitates the viral transmission. Frequent outbreaks in Europe, North America and Asia are reported during racing seasons. Less seasonal impact is seen in tropical areas where horses are kept outdoors year-round.
Similarly, Canine and Feline Influenza has more prevalence in the cold seasons due to the close indoor housing in these months. Seasonal outbreaks is linked to pet adoption spikes and kennel boarding. It is reported mostly in urban centers for greater pet keeping. Marine Mammal Influenza incidences in seals & whales rise in the winter months in temperate and polar regions. Higher population density of these mammals in breeding areas facilitates the outbreak. Seasonal patterns vary, with most outbreaks occurring in colder months due to increased animal density, migration and virus stability. Monitoring these trends is crucial to preventing outbreaks and potential zoonotic spillovers.
Global burden of seasonal influenza on humans and livestock
Seasonal influenza impact on both humans and livestock is prominent and is a challenging aspect for public health and livestock productivity. It is caused by influenza viruses (mostly types A and B), is a cause of numerous annual illness, hospitalizations, and deaths. Though the infection being seasonal, it is a serious public health concern globally. World Health Organization (WHO) stated that seasonal influenza infects around 1 billion people globally each year. There are 3 to 5 million serious cases of seasonal influenza annually resulting in 290,000 to 650,000 deaths related to respiratory dysfunction and distress worldwide. Worldwide influenza pandemics has occured invariably with unpredictable emergence of new infuenza A virus subtypes. The 1918 `Spanish flu A(H1N1) pandemic was more severe, causing around 20 million deaths worldwide, while the recent ones, A(H2N2) `Asian flu’ in 1957 and A(H3N2) `Hong Kong flu’ in 1968, were more subtle with moderate mortality. Since 1968, influenza A(H1N1), A(H3N2) and B strains have been recurring and causing overlapping epidemics each season. The recent 18 human cases of avian A(H5N1) influenza in Hong Kong and the high fatality were a ticking clock that another pandemic with heavy global morbidity and mortality is at our doorsteps. According to the recent study on the pattern of recurrence of the influenza pandemic, it can be noticed that a new strain causes a pandemic in every 30 years.
Economically influenza adds a lot of burden to the society including direct costs including the treatment, vaccination and health care costs and indirect costs due to loss in livestock productivity or generally human losses due to illness and premature death. There is a significant burden on the global economy affecting a country as a whole and also individually due to rising hospitalization costs, medical bills and an economic tension on the workforce.
Population of the extreme ends of age are most susceptible along with pregnant women and immunocompromised individuals. The seasonal flu occurs as an epidemic seasonally mostly occurring in the colder regions but there is always a variation in region and timing. With the ability of the virus to mutate by antigenic drift, the global vaccine coverage remains suboptimal. Still, vaccination and immunization is the most effective way to curb seasonal influenza and reduce its infectivity and virulence.
Impact of Seasonal Influenza on Livestock
Seasonal influenza is not only a problem of humans but also have a significant effect on animals, mostly pigs and poultry, that are highly susceptible to the virus. Influenza viruses are zoonotic and has a history of transmission between animals and humans, leading to both direct and indirect effects.
Swine influenza causes an enormous concern in pigs (swine), causing respiratory problems and putting a major economic strain on the pig rearing industry. H1N1 and other strains of the flu virus has pigs as its natural host and can lead to reduced productivity, fecundity and feed conversion ratio in herds, leading to reduced growth rates with excess requirement of feed, housing and other resources for their care. Due to its zoonotic nature it poses a viable threat to the human population with an ability to cause future human influenza pandemics.
Poultry (chickens, turkeys, etc.) are usually succumbed to avian influenza viruses (e.g., H5N1, H7N9), causing mass death in bird populations. The avian flu is an extremely infectious and contagious among poultry leading to economic devastation in the industry as it requires to cull infected animals causing restrictions on trade. Various strains, particularly H5N1 and H7N9, bear the potential to infect humans, leading to sporadic outbreaks high morbidity and mortality. Influenza viruses in animals is an evolving disease with the potential to cross over to humans and thus leading to new strains and serotypes that may lead to a new pandemic.
Public Health Implications of Seasonal Influenza
Influenza puts a significant pressure over healthcare systems, resulting to increased outpatient visits, hospitalizations, and intensive care unit (ICU) admissions. During flu seasons, health centres face limited bed issues and healthcare workers experience increased workloads. The economic burden is substantial, with costs related to treatment, lost productivity, and hospitalization. In severe cases, overwhelmed healthcare systems may struggle to provide minimum care.
Vaccination can be seen as the most effective method to prevent influenza and reduce complications. Annual flu vaccines are updated based on current virus strains. Public health campaigns promote vaccination and preventive behavioral steps, such as hand hygiene, mask-wearing, and avoiding close contact with affected individuals. Antiviral medications like zanamivir and oseltamivir helps subside duration and severity of illness if administered early.
Surveillance forms a important role in tracking influenza trends and informing public health responses. The WHO’s Global Influenza Surveillance and Response System (GISRS) watchout for virus activity worldwide, helping to identify emerging strains and guide vaccine development. National health agencies use data derived from surveillance programs to carry out timely interventions and allocate resources effectively.
Although seasonal influenza is a repetitive public health issue, the potential it has to evolve into a pandemic is a major concern. Previous outbreaks, such as the H1N1 pandemic in 2009, stresses on the need for robust preparedness plans. Governments and health organizations transform influenza surveillance into broader pandemic preparedness strategies, ensuring rapid response measures such as travel restrictions, vaccine distribution, and public health advisories. Even after the availability of preventive measures and vaccines, vaccine hesitancy persists a challenge due to fear of side effects and fake information. Public perception of influenza risk varies, with some individuals not serious about its severity. Effective communication strategies, including community engagement and media campaigns, are crucial to increase vaccine uptake and promoting responsible health behaviors. Seasonal influenza acts as a impending threat to public health, calls for coordinated actions to reduce its impact. Surveillance, vaccination, and public health interventions are crucial in reducing disease burden and preventing severe outcomes. Strengthening healthcare infrastructure, working on vaccine hesitancy, and increasing pandemic preparedness will help mitigate future influenza outbreaks and protect global health.
Influenza future directions and preparedness
Future directions and preparedness for influenza focus on improving surveillance, vaccine development, antiviral treatments, and global coordination to mitigate seasonal outbreaks and potential pandemics. By enhanced Surveillance and Early Detection we can strengthen global monitoring systems (e.g., WHO’s Global Influenza Surveillance and Response System).
We can utilize AI and big data for real-time outbreak predictions and can also expand genomic sequencing to track virus evolution and mutations. Vaccine Development for influenza can be done to provide long-lasting protection.We can improve vaccine production technologies (e.g., mRNA vaccines, cell-based or recombinant vaccines) and enhance vaccine distribution and coverage, mostly in low income regions. Antiviral and Therapeutic Innovations that is, developing next-generation antivirals to fight drug-resistant strains, exploring monoclonal antibodies and immune-modulating therapies and improving stockpiling , distribution strategies for antiviral medications are effective ways of controlling influenza.
Pandemic Preparedness Plans should be made earlier thus strengthening national and international pandemic response . We can also enhance healthcare system, increase hospital capacity & also conduct regular pandemic simulation exercises, so that people can combat flu. Increasing public awareness and vaccine confidence, implementing effective non-pharmaceutical interventions (e.g., masking, social distancing in severe outbreaks), strengthening communication strategies so that people get the correct information and avoid misinformation can also help in curbing flu. One Health Approach can also be taken by monitoring animal reservoirs (e.g., birds, pigs) for zoonotic influenza threats. We can develop strategies to mitigate the risk of avian and swine flu spillover to humans.
Challenges In Preventing Influenza Outbreak
Influenza outbreak management and prevention in livestock is challenging and has various constraints for several reasons. Mainly avian influenza (bird flu) and swine flu, are more prone to mutations and variations making it complex to provide long-lasting effective vaccines or treatments. The virus evolves rapidly, forming new strains that can not be covered by present vaccines. Influenza viruses are transmissible between species (e.g., from birds to pigs, or from pigs to humans), making their isolation and containment more hard and tedious. The cross-species transmission influences and increase the risk of antigenic drift and a new viral strain that is more virulent or even infects humans (zoonotic transmission), which poses a public health risk. Some animals carries the virus without any gross symptoms and signs making the art of diagnosis and identification a difficult task. Influenza spreads quickly in crowded conditions, where animals are in close contact with one another. The international import and export of livestock, feed, and animal products and by-products increases the risk of viruses spreading across borders. Infected animals or contaminated products can be exported, causing outbreaks in regions far from the original source. This movement across the globe makes containment effort difficult.
Effective surveillance and supervision systems are lacking in some regions, causing late detection of the influenza outbreaks. Ensuring vigorous biosecurity measures on farms can be a tedious task, exclusively in areas with limited resources or knowledge. Outbreaks usually needs culling infected or exposed animals, which can be expensive for farmers and the economy. Additionally, trade limitations and curtailment can be imposed on regions affected by outbreaks, further intensifyingg the economic consequences. In some cases, antimicrobial drugs are used to tackle or treat secondary bacterial infections in livestock primarily infected with influenza. However, antibiotics overuse can leads to antimicrobial resistance, complicating efforts to manage bacterial infections in both animals and humans.
Influenza viruses can persevere in the environment under certain explicit conditions, such as cold weather. Efficacious control requires cooperativeness between different aspects of government (local, national, and international), the agricultural sector, veterinarians, and public health organizations. Eradication of worldwide virulent influenza strains is so far unsuccessful and outbreaks are still in masses in all sectors of livestock. If the outbreak is early, it is better to cull the whole herd or flock. But for developing countries like India stamping out policy is not feasible. So at present isolating the animals with low mortality and culling them if the conditions demands.
Along with protection, vaccination also decreases virus shedding and thus reducing the viral load in the environment. But at the down side, vaccination built immunity in a population forces the virus for an antigenic drift forming new strains capable to escape the vaccination-induced immunity and continue to spread. Therefore, effective vaccination programs require close-meshed supervision, which adds to the costs of purchasing, distributing, and applying the vaccines. Each and every farm is a separate entity. A suitable risk analysis system has to be used for verifying and assessing the biosecurity risks. Promoting regional trading rather than inter-district or inter-regional or international trading and avoiding the livestock of different sources can help.
Conclusion:
Seasonal influenza is a global concern which adversely affects both human and animal populations. The spread of influenza viruses among animals can have serious consequences for public health. By strengthening monitoring and surveillance systems, increasing vaccination programs and fostering collaboration between human and veterinary officials, we can control and prevent the impact of influenza to a great extent. Veterinarians are front line warriors in monitoring and managing influenza in animals as they provide valuable information which helps prevent the incidence of new human flu strains. One Health approach integrating efforts across human, animal and environmental health sectors is the most efficient strategy in addressing the challenges induced by seasonal influenza. With ongoing research, collaboration and strict surveillance, we can definitely protect both our animal and human populations from the ever-evolving threat of seasonal influenza.
References:
- World Health Organization (WHO). (2020). Influenza (Seasonal). Retrieved from https://www.who.int/news-room/fact-sheets/detail/influenza-(seasonal)
2.Centers for Disease Control and Prevention (CDC). (2022). Burden of Influenza. Retrieved from https://www.cdc.gov/flu/about/burden/index.html
- Global Influenza Surveillance and Response System (GISRS). (2021). Influenza Global Update. Retrieved from https://www.who.int/teams/global-influenza-programme
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