What is G4 (and should we be worried)?

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The last thing anyone wants to hear about is another potential pandemic. Yet, a study recently published in the Proceedings of the National Academy of Sciences (PNAS) has created a great deal of worry. It’s about a novel group of swine flu strains that researchers say have the capability to spread to humans. Here’s what we know.

What is the G4 swine flu?

The group of viruses discussed in the PNAS study are referred to as the “G4” Eurasian (EA) avian like H1N1 viruses—or, just “G4” for short. They are a specific type of swine flu (caused by the influenza A virus) that’s spreading among pigs in China. There are four main types of influenza viruses (A, B, C, and D). Influenza A is the most common group to cause pandemics.

After the swine influenza virus caused the 2009 pandemic, Chinese government agencies partnered with the World Health Organization and scientists from universities in China and Britain to track and observe pig populations for signs of a virus with pandemic potential. 

That surveillance found a total of 179 swine samples that were deemed positive with an influenza A virus, and since 2016 the G4 H1N1 swine flu virus has been the most commonly isolated virus. While the recent media coverage is the first the general public may be hearing of the G4 swine flu—it isn’t entirely accurate to call it “new.”

Could G4 cause a human pandemic?

G4 has some new genetic components when compared to known flu strains. But it’s the similarities to the 2009 H1N1 virus behind the swine flu pandemic that are worrisome. 

1. It can infect humans.

Like the 2009 H1N1 virus, the G4 virus is able to attach to cells in human lungs, which allows it to cause infection in people. Not all swine flu viruses do so, which is why not every swine flu causes human infection.

In fact, this study proved the ability of the virus to infect people by testing to see if people working with the pigs had developed antibodies to the virus. From 2016 to 2018, 10.4% of swine production workers tested had antibody positivity (meaning infection had occurred). 

2. Most people would lack immunity.

Like the 2009 H1N1 virus, the G4 viruses are reported to have a combination of genes from influenza viruses found in humans, birds, and pigs. This could be the result of reassortment, a process when several viruses mix within a host—in this case a pig—exchange genetic material, and create a new influenza virus with new features. When a new virus emerges, most people lack immunity to it and are more prone to infection. The 2009 H1N1 pandemic virus was the result of a reassortment event.

3. It could disproportionately affect young people.

There are a few other concerning findings of this study, including a higher antibody positivity rate observed among younger 18 to 35 year old swine workers (versus older workers). This could represent a disproportionate infectivity of what is generally considered a healthier and less susceptible patient population, which raises alarm since the 2009 H1N1 pandemic caused the majority of deaths in the 18 to 64 years of age population.  

4. People without direct contact to pigs were infected.

Antibody positivity to G4 flu was also found in 4% of a 230-person sample from the general population in China that didn’t have direct contact with the tested pigs. This bears similarity to the 2009 H1N1 pandemic in which the initially identified patients had no known contact with pigs.

5. It spreads by contact or respiratory droplets.

In addition, laboratory findings show that the virus can spread by direct contact or respiratory droplets. This type of transmission, combined with lack of protection to this specific G4 influenza strain from currently available human influenza vaccines are also components of a virus with pandemic potential. 

How concerned should we be?

First, we need to break down some of the numbers a little further. 

It affects a small percentage of the population.

While there were 179 positive samples of the tested pigs, this actually represents a very low isolation rate. Of the 179 positive test results, 136 came from a population of nearly 30,000 nasal swab samples of non-symptomatic pigs. This represents an isolation rate of 0.45%. The remaining 43 positive samples of the total 179 positives samples came from a population of just over 1,000 nasal swabs or lung samples collected from pigs exhibiting respiratory symptoms for an isolation rate of 4.23%. In addition, the total number of pigs tested represents a very small number of the total population of pigs in China—which may be as many as 500 million. 

There’s no known transmission between people.

Currently, no known transmission has been observed with the G4 swine flu between people. A pandemic can only occur when person-to-person transmission takes place. History teaches us that this transmission from pig to human—variant viruses—that has been observed with the G4 swine flu does occur to some extent every year with other influenza viruses, but is usually not sustained. Right now, we don’t have good reason to think this G4 swine flu will cause anything different. Lastly, we know that behaviors, like eating pork, does not allow for a virus infection to spread from pig to human. 

It hasn’t reached the United States yet.

At present, the Centers for Disease Control and Prevention (CDC) has verified that G4 viruses haven’t been detected in pigs or humans in the United States.

With that said, this novel G4 swine flu virus has similarities to the 2009 H1N1 pandemic strain, so there does need to be some level of concern. Ongoing circulation in pigs with continued exposure to people may allow for further exchanges of genetic material—also known as reassortment—to occur, which could allow the virus to become more fit to cause a pandemic. Meaning, it could transform further and become easier to transmit from person to person.

What is the U.S. doing to prepare?

The CDC is currently taking the following steps: 

• Working with public health officials in China to obtain a sample of the virus
• Using their Influenza Risk Assessment Tool (IRAT) to assess the risk of this virus causing a pandemic
• Evaluating where current vaccines being studied against related flu viruses might protect against this virus
• Evaluating if the existing flu antiviral medications offer protection against this virus

The 2009 H1N1 influenza pandemic was the first pandemic in almost 40 years. The 2009 H1N1 flu virus that caused it was highly transmissible—to the tune of 60.8 million cases in the U.S. in its first year and almost 12,500 deaths. But, the fatality rate was low compared to previous pandemics, partially due to an improved understanding of flu transmission and viral control measures. 

The U.S. response to the 2009 H1N1 pandemic was robust and multi-faceted, lasting over a year; without such a response, many more lives would have been lost. The silver lining of the recent COVID-19 pandemic is the insight the world is able to gain from this strong response, to apply to future pandemics. 

How to stay healthy

We know that persons infected with influenza are contagious for a fairly long period—usually a couple of days before flu symptoms start all the way to five days after getting sick. We also know that the virus can be spread through the air in droplets from coughing or sneezing by an infected person, or even by touching surfaces on which these droplets land and then touching your face.

Important precautions to take include those everyone is very familiar with thanks to the current coronavirus pandemic:

• Practice good handwashing strategies and use hand sanitizer
• Avoid touching your face
• Keep shared spaces clean
• Avoid sick people (and avoid people if you are the one to become sick!)
• Cover your coughs and sneezes to prevent further spread
• Get vaccinated

A seasonal flu vaccine, every single year, is one of the most crucial steps you can take to stay flu-free. Flu vaccines are some of the most accessible vaccines. They are available at many retail pharmacies and are typically covered by insurance. Routine vaccination is recommended for all persons greater than 6 months old, unless you’re otherwise instructed by your healthcare provider. There’s a lot of misleading information about reasons to avoid the flu shot, but it’s important to get a new flu shot every flu season. 

RELATED: Can pregnant women get the flu shot?

Is there a vaccine available for the novel G4 swine flu?

The current flu vaccine doesn’t protect against G4. However, the CDC is working to determine if a prototype vaccine against a closely related swine flu virus offers cross-protection against G4. If not, the CDC will begin work on a new flu vaccine that will protect against the new swine flu.  

If 2020 has taught the world anything, it should be the importance of good handwashing hygiene and social distancing. If you’re sick—no matter the cause—you shouldn’t be going to work or school, and should be limiting contact with others. 

It is important to be on alert for new viruses with the potential to cause a pandemic. Our experience with the 2009 H1N1 pandemic and now with the COVID-19 pandemic has set a strong foundation in understanding how quickly things can escalate, and what has and has not worked in terms of a response. While currently available information on the G4 swine flu isn’t enough to cause full-blown panic, we can’t have tunnel-vision with coronavirus and must continue to be aware of the threat of new strains of infectious disease.