Bird flu: are viruses still in the air?

Bejing. Bird flu is transmitted in various ways and the process needs to be studied in depth. Sojourner in a Strange Land/Flicker, CC BY-NC-SA

Bird flu: are viruses still in the air?

Avian influenza, also called “bird flu”, is a disease caused by viruses transmitted from poultry to humans, sometimes going by way of pigs. There are several strains of the virus, noted by H and N for the proteins that determine the entrance and release of the virus in the cell.

In Europe, the H5N8 virus has raised alarm since 2016, leading to massive cullings in poultry farms. Similar outbreaks and cullings took place in Japan, Saudi Arabia and Zimbabwe, but so far the disease has not been transmitted to humans.

By contrast, the H7N9 virus, which appeared in China in 2013, spreads from poultry to humans and, according to health authorities, has killed 40% of the people it infected. The H5N1 virus, which emerged in Hong Kong in 1997, has killed approximately 66% of those it has infected.

Journalists have described what they have called “bird-flu fatigue” in countries at risk, when questions are raised as to why so much energy is spent on a family of viruses less dangerous than Ebola or HIV/Aids. But if bird flu is less present in the media, the viruses that cause it are still in the atmosphere. The scientific question continues to fascinate experts: under what conditions can these viruses be transmitted from birds to humans by aerial particles, and what will be the consequences for those who are not immune? Providing answers requires analysing the daily relations between humans, birds and viruses, beyond media alerts and animal cullings.

An air pump in the poultry markets in China

Hui-Ling Yen, a virologist at the University of Hong Kong’s School of Public Health, conducted research between December 2015 and July 2016. Her studies, published in journals such as Building and Environment, European Communicable Disease Bulletin and Emerging Infectious Diseases, seek to measure the concentration of avian influenza virus in poultry markets in southern China.

In this region, live poultry are purchased by consumers and slaughtered on the spot by vendors, increasing the risk of the transmission of the bird flu to humans. Hui-Ling Yen applied a portable air-sampling device developed by the US National Institute for Occupational Safety and Health (NIOSH). Placed on a tripod 1.20m from the ground for 30 minutes, the air pump can capture viral particles in a liquid-filled tube. This liquid is then analyzed in the laboratory using the PCR technique to measure the genetic diversity of the viral strains.

While correlated with more conventional analyses performed by oral and cloacal sampling on poultry, the new method has several advantages. First, it is non-invasive, which means it doesn’t involve handling animals, and is therefore better accepted by sellers. Second, it is faster, since it is no longer necessary to take a sample from each bird, and provides a diagnosis of an entire seller’s stall. Above all, it measures the risk of contagion for those who enter the stall area, not just those who directly touch the poultry.

Viral particles

Poultry market, Tai Po, Hong Kong. Bought alive, the chicken is killed in front of the customer. Frédéric Keck, Author provided

Using this method, the research team has come up with several interesting results. For example, the machines commonly used at live poultry markets in Southeast Asia to defeather poultry for clients may dramatically increase the amount of virus-laden particles in the air. When considering live poultry markets as potential sources of virus-laden emissions in densely populated urban cities, they also modeled the potential dispersion of airborne particles within a 100-metre radius depending on the direction of the wind.

Hui-Ling Yen also investigated how influenza is transmitted in the laboratory using ferrets, whose flu symptoms are closest to those of humans. After working with engineers to design a transmission chamber capable of separating airborne particles by size, she distinguished large and fine particles. Large ones cannot spread far from the source of infection because of gravity, and they can be blocked by surgical masks and careful hygiene. Fine particles (less than 1 micrometer in diameter) can remain suspended in the air and spread to a wider area without being stopped by classical prevention means.

A risk of transmission higher than elsewhere

Studies involving the detection of airborn avian influenza viruses have previously been conducted in the Netherlands in 2014. They were also conducted in Taiwan in 2009 to measure the impact of dust clouds coming from mainland China.

Such methods had never been applied in mainland China itself, where the risk of transmission of bird-flu viruses to humans is higher than elsewhere.

Chicken being plucked before the Chinese New Year in the Tiexi District, Anshan, Liaoning Province, China (February 2008). Sonya Sonya/Flickr, CC BY-ND

Hui-Ling Yen’s studies rely on a collaboration with the Guangdong Provincial Centers for Disease Control and Prevention. This collaboration shows that, just as with the air pollution emitted by cars, the Chinese government and its population are aware of the negative impacts that accelerated development can have on the atmosphere the country’s residents breathe.

Bird flu thus reveals the threats that the development of industrial farming and car transportion are hovering in the air.

An artist following virologists in Vietnam

Lena Bui, a Vietnamese artist trained in the United States and Japan, provides another perspective on the threat of bird flu. She collaborated with Oxford University’s Clinical Research Center in Ho Chi Minh City in the context of the first outbreaks of avian influenza in Vietnam after 2005. She then followed the activities of virologists in their laboratory discussions and their surveys of poultry farms. She finally chose to show, rather than the virological conceptions of scientists, the farmers’ practices in dealing with farm animals.

In 2012, Lena Bui discovered a 2005 newspaper photograph showing a woman in work clothes that were covered with feathers: “She looked like a big ostrich”, the artist stated during an interview. “I like this moment, when the boundary between humans and animals is blurred”. The article focused on a village in northern Vietnam, Trieu Khuc, where duck feathers are sorted and exported to China. Because of the risk of bird flu, China stopped importing feathers, and the village had to reorganise. Lena Bui continues:

“The news were sensationalising. I went there and people told me no one got sick. When you have daily contact with feathers, maybe you develop some form of immunity. It’s a place that stimulated my imagination.”

We thank Lena Bui for giving access to readers of The Conversation to her video. Click on the link to access it.

The artist made a short film installation titled “When Birds Dance Their Last”, presented in 2012 at the Ho Chi Minh City Museum and in 2013 at the Wellcome Collection in London as part of the exhibition “Voracious Embrace: The Human/Animal Interface”.

Trieu Khuc’s village, from ‘Where Birds Dance their Last’. Lea Bui, Author provided
Trieu Khuc’s village, from ‘Where Birds Dance Their Last’. Lena Bui, Author provided

The slow movements of defeathering workers

The film shows on two panels the workers drying feathers in slow movements on the background of aerial music, with comments made by workers themselves on this practice passed down through the generations. The film begins with the strange image of feathers on which flies vibrate, then introduces a masked woman under a pointed hat ventilated by a fan. The villagers invoke the tradition, the length of marriages celebrated at the temple, the presence of ancestors in nearby graves.

In 2016, Lena Bui made another 45-minute film, designed more as a docu-fiction than as a film installation.

We thank Lena Bui, for giving access readers of The Conversation access to her video for six weeks. Click on the link to access it.

She followed the virologists on a pig farm in the Mekong Delta in Vietnam – also considered as a major source of influenza transmission between animals and humans. She received a family’s agreement to welcome a professional actress in their house. The actress plays a niece who comes from the city to visit her aunt, and asks her to show the traditional techniques of raising pigs. The niece wants to know the taste of the meat before industrial breeding under state regulations. Her aunt resists but eventually agrees. The film’s tipping point is reached when wholesalers coming to buy pigs justify lowering the price they pay through the use of chemicals on neighboring farms. Rather than avian or swine flu, this film shows the tensions in the daily practices of farmers in their relations with the state and the market.

The research of Hui-Ling Yen and Lena Bui show, with the help of virology and cinematography, that influenza viruses are in the air, in the sense that they reveal how the transformations of relations between humans, birds and pigs in East Asia are changing the atmosphere of the globe.


Hui-Ling Yen, Lena Bui and Frédéric Keck, author of this article, have each received funding from the Axa Research Fund, to improve public knowledge about pandemic risks.

This article was originally published in French

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