Christopher Labos: Avian flu has spread to dairy cows. Is our milk safe?

The recent detection of H5N1 in cattle is concerning, but pasteurization exists for exactly this reason. Just don’t drink raw milk.

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The recent united states reports The detection of the H5N1 virus in the milk supply is concerning. It means that the bird flu has spread to dairy cattle and it was probably spreading undetected since late December, long before the first case reported in March. This does not mean that the milk supply is unsafe.

The concern with H5N1 (aka bird flu) is its potential to infect humans. It is not known to what extent this should be of concern.. There has been a relatively small number of human cases of H5N1 since 1997. Most cases were from birds to humans and occurred in people who were in close contact with infected birds, especially poultry. Transmission from person to person has occurred, but not in a sustained manner. H5N1 still primarily infects birds. It has not yet acquired the ability to spread easily among humans.

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But its recent detection in cattle is worrying. If it can now easily infect cows and other mammals, it may soon gain the ability to more easily infect and, more importantly, spread directly among humans.

But a lot has to happen before that becomes a reality, and it’s unclear how worrying a human outbreak of H5N1 would be for human health. Human cases to date have been fairly severe overall, but there has also been a spectrum of illnesses with mild cases.

We also have tools at our disposal to combat any possible pandemic. We have vaccines against the flu, and specifically against H5N1, and also antivirals to treat severe cases. H5N1 may not reach humans, but emergency preparedness is about preparing for a possible emergency while also hoping that the plan never has to be implemented. We practice school fire drills not because we expect schools to burn down, but because we want to be prepared in case it happens.

Recent reports of the detection of H5N1 in cows and commercially available milk are obviously concerning. But we pasteurize our milk for exactly this reason. While genetic traces of the virus were found in the milk using PCR testing, there was no live virus capable of causing an infection. That means pasteurization was effective in inactivating the virus. Therefore, the milk supply is safe and there is no need to worry about transmission of the virus through dairy products. Unless you drink raw milk.

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Occasionally raw milk becomes popular as a health fad and people claim that it is healthier than pasteurized milk. Some claim that pasteurization is dangerous, which it obviously isn’t, since it basically amounts to heating the milk long enough to kill the microbes. Heat does not destroy minerals such as calcium and pasteurization does not deprive milk of its health benefits. If anything, raw milk is worse for you because it doesn’t contain vitamin D. We supplement our milk with vitamin D to prevent deficiencies.

But the real danger of raw milk is its ability to transmit diseases. At the beginning of the 20th century, the problem was tuberculosis… and the spread of bovine tuberculosis through contaminated milk was a major health problem. While tuberculosis is much rarer today, salmonella, E. coli, Listeria, and other bacteria still make people sick. Pasteurization minimizes the chance of food outbreaks like this.

It is unclear whether H5N1 in milk could infect humans. However, first reports discovered that cats living on farms with infected cows became ill after drinking raw milk from infected cattle.

But this is not something consumers need to worry about right now. Adequate testing of imported livestock and dairy products, destruction of milk from infected cows, and standard infection control measures should preserve the safety of the food supply. The final step, pasteurization, ensures that the milk is safe to drink and disease-free. Therefore, we can be fairly confident in saying that the milk supply is safe. Just don’t drink raw milk.

Christopher Labos is a Montreal doctor, co-host of the show Body of Evidence Podcast, and author of Does coffee cause cancer?

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