H1N1 Influenza COVID-19 Comparison: Similarities and Differences

Before we compare the two pandemics in more detail, here are some quick facts about each.

Let’s look at some similarities between the 2009 H1N1 flu and COVID-19 pandemics.

Transmission

Both H1N1 flu 2009 and COVID-19 can be transmitted in similar ways. These include:

• Breathing drops. These are small droplets that are made when someone talks to the virus, sneezes or coughs. If you inhale these drops, you can catch the virus.
• Contaminated objects. Breathing drops containing viruses can end up on things like counters and doorknobs. You can catch the virus by touching these things and then touching your mouth, nose or eyes.

It is also possible for someone to pass both viruses if they have no symptoms. This is called asymptomatic transmission.

Symptoms

Both 2009 H1N1 flu and COVID-19 are respiratory infections that have many common symptoms. This may include:

One symptom unique to COVID-19 is loss of odor and taste.

The 2009 H1N1 flu and COVID-19 can range from mild to severe. In both pandemics, certain groups were at increased risk for serious diseases.

Risk factors

The groups at risk for complications from 2009 H1N1 influenza and COVID-19 have a significant overlap. These include:

• adults 65 years and older
• pregnant people
• those with certain types of underlying health conditions

Underlying health conditions that can contribute to complications include:

Additional high-risk groups for 2009 H1N1 flu

Some additional groups that at a higher risk for serious illness during the H1N1 flu pandemic in 2009, including:

• children under the age of 5
• people under the age of 19 who received long-term aspirin therapy

Additional high-risk groups for COVID-19

In addition, people with the following underlying health conditions at a higher risk for serious illness from COVID-19:

Complications

Both 2009 H1N1 flu and COVID-19 can lead to similar complications, including:

COVID-19 also has some additional complications, including:

Vaccination

Following the emergence of 2009 H1N1 flu and COVID-19, rapid attempts were made to develop a vaccine.

During the 2009 H1N1 flu pandemic, a total of five vaccines have been approved by the Food and Drug Administration (FDA). These vaccines have been developed using the same technology previously used for seasonal flu vaccinations.

According to the World Health Organization (WHO), more than 200 COVID-19 vaccine candidates are in development at the time of this article, with at least seven different vaccines currently in use worldwide. They use a variety of different technologies, including:

Three vaccines are currently approved by the FDA for emergency use in the United States. These include the vaccines provided by:

Let us now examine the differences between the two pandemics.

The type of virus

The H1N1 pandemic in 2009 was caused by a flu virus. Influenza viruses are part of the viral family Orthomyxoviridae. Their genetic material consists of eight separate strands of RNA.

This particular flu virus jumped to humans from pigs in 2009, hence the monk ‘swine flu’. It actually contains RNA strands of human, porcine and avian origin. How does this happen?

Pigs can get different types of flu virus. When this happens, the RNA strands of the different viruses can mix together through a process called reassortment. It can create a unique flu virus, like the 2009 H1N1 virus.

COVID-19 is caused by a coronavirus from the viral family Coronaviridae. Its genetic material consists of a single strand of RNA. The specific virus that causes COVID-19 is called SARS-CoV-2.

The exact origin of SARS-CoV-2 is still unknown. A recently released report from the WHO suggests that SARS-CoV-2 probably originated in bats and was transmitted to humans by an unknown intermediate host.

2009 H1N1 flu today

Although the H1N1 flu pandemic ended in 2009 in 2010, these viruses still remain in circulation as seasonal flu strains. It has been included annually as one of the components of the seasonal flu vaccine since the pandemic.

Global deaths

In a 2012 study, researchers estimate that approximately 284,000 deaths worldwide occurred in the first 12 months of the 2009 H1N1 flu pandemic. Since the end of the pandemic, the Centers for Disease Control and Prevention (CDC) has estimated that it is an additional factor 75,000 deaths have occurred in the United States due to 2009 H1N1 flu.

COVID-19 has caused significantly more deaths worldwide. It is estimated that approx. 2,000,000 deaths of COVID-19 occurred in the first 12 months of the pandemic.

As with the H1N1 flu in 2009, COVID-19 deaths will continue during and after the pandemic. At the time of writing, COVID-19 has caused nearly 3,000,000 deaths worldwide. More than 500,000 deaths have occurred in the United States.

Contagion

COVID-19 is more contagious than H1N1 flu from 2009. This means that COVID-19 can spread more easily between individuals.

It is estimated that the R₀ for COVID-19 is about 3 while the R₀ for 2009 the H1N1 flu is between 1.3 and 1.7. ‘R₀”Stands for basic reproduction number. This reflects the number of other people who are susceptible to contracting the virus if one person has it.

Thus, one person who developed COVID-19 could possibly transmit the virus to three other people. Meanwhile, someone with H1N1 flu 2009 can transmit it to one to two other people.

The period of infection between the two viruses can also vary:

• Flu: A person who has flu can usually pass the virus from 1 day before the onset of symptoms to 5 to 7 days after becoming ill.
• COVID-19: COVID-19 can be passed about 2 days before the onset of symptoms. Whether there are symptoms or not, a person can pass the virus up to ten days after testing positive.

Symptoms begin

Influenza, including the 2009 H1N1 flu, and COVID-19 differ when it comes to starting symptoms:

• Flu: The incubation period for influenza may vary from 1 to 4 days. When symptoms occur, they suddenly appear.
• COVID-19: COVID-19 has a longer incubation period, ranging from 2 to 14 days, although many people develop symptoms 5 days after you contracted the virus. Symptoms usually occur gradually.

Age group affected the most

The two pandemics also differed in the age groups most affected:

• 2009 H1N1 flu: People under the age of 30 was most affected by the 2009 H1N1 flu pandemic. It is believed to be due to the existing immunity to flu in older people.
• COVID-19: Adults 30 and older were most affected by the COVID-19 pandemic. In general, fewer and fewer serious cases were observed in younger people.

Severity of diseases

It is estimated that between 94 and 98 percent cases of 2009 H1N1 flu were mild. Far fewer people experience serious or critical illnesses.

A higher percentage of people who develop COVID-19 have serious illnesses. The WHO estimates that although COVID-19 is mild 80 percent of the time, 20 percent of people who contract the virus can become seriously or critically ill.

Treatments

Treatment for 2009 H1N1 flu included supportive care and antiviral drugs. Supportive care involves:

• get enough rest
• drink plenty of fluids
• Use OTC medications such as paracetamol (Tylenol), ibuprofen (Advil, Motrin) and naproxen (Aleve) to relieve symptoms such as fever and pain

The H1N1 virus was also susceptible to antiviral drugs previously used (and still used) for seasonal flu, such as oseltamivir (Tamiflu) and zanamivir (Relenza).

When COVID-19 first appeared, however, we did not know of any treatments that were effective against it. Over time, various therapies have been or are approved by the FDA for emergency use.

Mild to moderate COVID-19 is often treated with supportive care. Additional treatments are also available for people who are hospitalized or at high risk for serious illness. These may include:

• remdesivir (Veklury), the only FDA-approved antiviral treatment for COVID-19
• SARS-CoV-2 neutralizing antibodies
• dexamethasone, a type of steroid medication
• COVID-19 recovery plasma

We experienced two different pandemics in the 21st century: the 2009 H1N1 flu pandemic and the COVID-19 pandemic. There are different similarities and differences between these two pandemics.

Although caused by different viruses, both H1N1 flu 2009 and COVID-19 are respiratory diseases that are transmitted in the same way. There is also a lot of overlap in symptoms, complications and risk factors for serious diseases.

However, COVID-19 is likely to cause more serious illnesses than H1N1 flu in 2009 and has led to more deaths worldwide. It is also more contagious than the 2009 H1N1 flu.

Although effective treatments were not known at the beginning of the COVID-19 pandemic, there are now a number available. In addition, as in the 2009 H1N1 flu pandemic, vaccines were rapidly developed for COVID-19.