Avian Influenza H5N1 Outbreak in US Dairy Herds: Low Public Health Risk, Vaccine Measures in Place

Core Concepts

The risk of avian influenza A subtype H5N1 to the general public remains low, and vaccine development measures are in place to address any potential outbreak.

Abstract

The content discusses the public health implications of the recent detection of avian influenza A subtype H5N1 in US dairy herds, which led to a cow-to-human transmission in Texas. Key highlights:

The CDC's Influenza Division director, Vivien Dugan, stated that the risk to the general public remains low, and vaccine development measures are in place should an outbreak occur.
The CDC has established candidate vaccine viruses, which can be used by manufacturers to produce new vaccines if needed.
The CDC is actively partnering with commercial diagnostic developers and testing companies to scale up testing capabilities in case of an outbreak.
The only current human case in the US was reported on April 1, and the person had direct exposure to cattle and reported mild symptoms, but has since recovered.
Since 1997, there have been 909 reported human cases of H5N1 infection globally, with about half resulting in death. However, only a small number of human cases have been reported since 2015, but more than two dozen have been reported since 2022.
In the US, the first detection of H5N1 was in wild birds in January 2022, followed by the first detection in a commercial poultry flock the next month. The first detection in dairy cattle was in March 2023.
Testing has shown that the virus remains an avian virus and has not become a bovine virus. The USDA has issued a federal order requiring the reporting of positive influenza tests in livestock and mandatory testing for influenza of dairy cattle before interstate movement.
The milk supply is considered safe, as nearly 99% of the commercial milk supply comes from farms that participate in the Grade A program and follow the Pasteurized Milk Ordinance, which outlines pasteurization requirements.
However, there are still many questions to be answered through research, such as the level of virus shedding by apparently healthy cows, the survival of live virus through pasteurization, and the effects on different dairy products.

Stats

Since 1997, there have been 909 reported human cases of H5N1 infection globally, with about half resulting in death.
Only a small number of human cases have been reported since 2015, but more than two dozen have been reported since 2022.
As of today, there are affected herds in 33 farms across eight states in the US.

Quotes

"The risk to the general public remains low," said Vivien Dugan, PhD, director of the Influenza Division at the Centers for Disease Control and Prevention (CDC).
"About half [52%] of the human cases have resulted in death."
"We haven't seen anything that would change our assessment that the commercial milk supply is safe," says Donald Prater, DVM, acting director of the Center for Food Safety and Applied Nutrition at the US Food and Drug Administration (FDA).

Key Insights Distilled From

Avian Flu Threat Still Low and Vaccine Measures Are Ready

by Marcia Frell... at www.medscape.com 04-26-2024

https://www.medscape.com/viewarticle/avian-flu-threat-still-low-and-vaccine-measures-are-ready-2024a100087p

Deeper Inquiries

What are the potential long-term implications of the H5N1 virus adapting to infect and spread among cattle?

The potential long-term implications of the H5N1 virus adapting to infect and spread among cattle are concerning. If the virus becomes established in cattle populations, it could lead to ongoing transmission within herds, posing a risk of further spillover to humans. This could result in more frequent cases of cow-to-human transmission, potentially leading to larger outbreaks or even a sustained epidemic. Additionally, the adaptation of H5N1 to cattle could complicate control measures and vaccine development efforts, as the virus may evolve in ways that make it more difficult to combat effectively.

How effective are the current pasteurization methods in eliminating the H5N1 virus from dairy products, and what additional measures might be necessary to ensure the safety of the milk supply?

Current pasteurization methods are generally effective in eliminating the H5N1 virus from dairy products, as pasteurization involves heating milk to temperatures that can inactivate most pathogens, including viruses. However, the detection of the virus in dairy cattle raises questions about the potential survival of the virus through the pasteurization process. Additional measures that might be necessary to ensure the safety of the milk supply include enhanced monitoring and testing of dairy cattle for the virus, implementing stricter biosecurity measures on farms to prevent transmission, and conducting further research to understand the viability of H5N1 in dairy products post-pasteurization. It may also be beneficial to explore alternative pasteurization techniques or additional safety protocols specific to H5N1.

Given the potential for zoonotic transmission, how can the scientific community and public health authorities work together to develop a more comprehensive and proactive approach to monitoring and mitigating the risks posed by emerging infectious diseases at the human-animal interface?

To develop a more comprehensive and proactive approach to monitoring and mitigating the risks posed by emerging infectious diseases at the human-animal interface, the scientific community and public health authorities can collaborate in several ways. Firstly, they can establish robust surveillance systems that monitor both animal and human populations for signs of emerging diseases, enabling early detection and response. Secondly, they can enhance communication and information sharing between veterinary and human health sectors to facilitate a coordinated response to zoonotic threats. Additionally, investing in research to better understand the dynamics of zoonotic transmission and the factors that contribute to spillover events can inform targeted interventions and control strategies. By working together, sharing data, and coordinating efforts, the scientific community and public health authorities can improve preparedness and response capabilities to effectively address the risks posed by emerging infectious diseases at the human-animal interface.