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SUNDAY SCIENCE: WITH ALL THIS BIRD FLU AROUND, HOW SAFE ARE EGGS,
CHICKEN OR MILK?  
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Enzo Palombo
June 5, 2024
The Conversation
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_ Recent outbreaks of bird flu – in US dairy herds, poultry farms
in Australia and elsewhere, and isolated cases in humans – have
raised the issue of food safety. _

, AS Foodstudio/Shutterstock

 

Recent outbreaks of bird flu – in US dairy herds
[[link removed]], poultry
farms in Australia
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and elsewhere, and isolated cases
[[link removed]]
in humans
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– have raised the issue of food safety.

So can the virus transfer from infected farm animals to contaminate
milk, meat or eggs? How likely is this?

And what do we need to think about to minimise our risk when shopping
for or preparing food?

How safe is milk?

Bird flu (or avian influenza) is a bird disease caused by specific
types of influenza virus. But the virus can also infect cows. In the
US [[link removed]], for
instance, to date more than 80 dairy herds in at least nine states
have been infected with the H5N1 version of the virus.

Investigations are under way
[[link removed]]
to confirm how this happened. But we do know infected birds can shed
the virus in their saliva, nasal secretions and faeces. So bird flu
can potentially contaminate animal-derived food products during
processing and manufacturing.

Indeed, fragments of bird flu genetic material (RNA) were found in
cow’s milk
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from the dairy herds associated with infected US farmers
[[link removed]].

However, the spread of bird flu among cattle, and possibly to humans,
is likely to have been caused through contact with contaminated
milking equipment
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not the milk itself.

The test used to detect the virus in milk – which uses similar PCR
technology to lab-based COVID tests – is also highly sensitive. This
means it can detect very low levels of the bird flu RNA. But the test
does not distinguish between live or inactivated virus, just that the
RNA is present. So from this test alone, we cannot tell if the virus
found in milk is infectious (and capable of infecting humans).

[Rows of milk bottles in supermarket fridge]
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It’s best to stick with pasteurised milk. Amnixia/Shutterstock
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Does that mean milk is safe to drink and won’t transmit bird flu?
Yes and no.

In Australia, where bird flu has not been reported in dairy cattle,
the answer is yes. It is safe to drink milk and milk products made
from Australian milk.

In the US, the answer depends on whether the milk is pasteurised
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We know pasteurisation is a common and reliable method of destroying
concerning microbes, including influenza virus. Like most viruses,
influenza virus (including bird flu virus) is inactivated by heat.

Although there is little direct research on whether pasteurisation
inactivates H5N1 in milk, we can extrapolate from what we know about
heat inactivation of H5N1 in chicken
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and eggs [[link removed]].

So we can be confident there is no risk of bird flu transmission via
pasteurised milk or milk products.

However, it’s another matter for unpasteurised or “raw” US milk
or milk products. A recent study
[[link removed]] showed mice fed
raw milk contaminated with bird flu developed signs of illness. So to
be on the safe side, it would be advisable to avoid raw milk products.

How about chicken?

Bird flu has caused sporadic outbreaks in wild birds and domestic
poultry worldwide, including in Australia
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In recent weeks, there have been three reported outbreaks
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in Victorian poultry farms
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(two with H7N3 bird flu, one with H7N9). There has been one
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reported outbreak in Western Australia
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(H9N2).

The strains of bird flu identified in the Victorian and Western
Australia outbreaks can cause human infection, although these are rare
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and typically result from close contact with infected live birds or
contaminated environments
[[link removed]-(h7n9)-virus-outbreak].

Therefore, the chance of bird flu transmission in chicken meat is
remote.

Nonetheless, it is timely to remind people to handle chicken meat with
caution as many dangerous pathogens, such as _Salmonella_ and
_Campylobacter_, can be found on chicken carcasses.

Always handle chicken meat carefully when shopping, transporting it
home and storing it in the kitchen. For instance, make sure no meat
juices cross-contaminate other items, consider using a cool bag when
transporting meat, and refrigerate or freeze the meat within two
hours.

Avoid washing your chicken
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before cooking to prevent the spread of disease-causing microbes
around the kitchen.

Finally, cook chicken thoroughly as viruses (including bird flu)
cannot survive
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cooking temperatures.

Are eggs safe?

The recent Australian outbreaks have occurred in egg-laying or mixed
poultry flocks, so concerns have been raised about bird flu
transmission via contaminated chicken eggs.

Can flu viruses contaminate chicken eggs and potentially spread bird
flu? It appears so. A report
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from 2007 said it was feasible for influenza viruses to enter through
the eggshell. This is because influenza virus particles are smaller
(100 nanometres) than the pores in eggshells (at least 200 nm).

So viruses could enter eggs and be protected from cleaning procedures
designed to remove microbes from the egg surface.

Therefore, like the advice about milk and meat, cooking eggs is best.

The US Food and Drug Administration
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recommends cooking poultry, eggs and other animal products to the
proper temperature and preventing cross-contamination between raw and
cooked food.

In a nutshell

If you consume pasteurised milk products and thoroughly cook your
chicken and eggs, there is nothing to worry about as bird flu is
inactivated by heat.

The real fear is that the virus will evolve into highly pathogenic
versions that can be transmitted from human to human
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That scenario is much more frightening than any potential spread
though food.[The Conversation]

Enzo Palombo
[[link removed]], Professor
of Microbiology, _Swinburne University of Technology
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This article is republished from The Conversation
[[link removed]] under a Creative Commons license. Read
the original article
[[link removed]].

Beyond the Tricks: The Science and Comparative Cognition of Magic
[[link removed]]
Elias Garcia-Pelegrin, Alexandra K. Schnell, Clive Wilkins, and Nicola
S. Clayton
Annual Review of Psychology  
Volume 75, 2024 

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