Influenza A virus subtype H1N1 facts for kids
Quick facts for kids Influenza A virus subtype H1N1 |
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Virus classification  |
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| (unranked): | Virus |
| Realm: | Riboviria |
| Kingdom: | Orthornavirae |
| Phylum: | Negarnaviricota |
| Class: | Insthoviricetes |
| Order: | Articulavirales |
| Family: | Orthomyxoviridae |
| Genus: | Alphainfluenzavirus |
| Species: |
Influenza A virus
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Influenza A virus subtype H1N1
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H1N1 (also known as A/H1N1) is a common type of influenza A virus, which causes the flu. This virus has two special proteins on its surface: hemagglutinin (H) and neuraminidase (N). These proteins help scientists classify different flu viruses, like H1N1 or H3N2.
H1N1 viruses are found in humans, pigs, and birds. Some H1N1 strains cause regular seasonal influenza in people each year. Other strains are found in pigs (swine influenza) and birds (avian influenza). The virus itself is tiny, about 80 to 120 nanometers wide.
Scientists think that modern H1N1 viruses might have come from the 1918 flu pandemic virus.
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Understanding Swine Flu
Swine influenza, or swine flu, is a breathing illness that pigs get. It's caused by the Influenza A virus. These viruses that usually live in pigs are called swine influenza viruses (SIVs).
Some common SIV strains include H1N1, H1N2, H3N1, H3N2, and H2N3. Pigs can also get infected with other types like H4N6 and H9N2.
Swine flu viruses are found in pigs all over the world. It's not common for the virus to spread from pigs to humans. When it does, it's called zoonotic swine flu. People who work closely with pigs have a higher chance of getting infected. But don't worry, properly cooking pork meat removes any risk of infection.
Scientists found that pigs infected with the H1N1 virus from the 2009 human pandemic showed flu signs within four days. The virus also spread to other pigs they were housed with.
Major H1N1 Outbreaks
H1N1 has caused several important flu outbreaks throughout history.
The 1918 Spanish Flu Pandemic
The 1918 flu was a very serious and deadly type of H1N1 avian influenza. It killed between 17 and 50 million people worldwide from 1918 to 1920. It was one of the deadliest pandemics in human history.
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The 1918 flu caused many deaths, especially among young adults. This might have happened because their strong immune systems reacted too powerfully to the virus. When the virus infected lung cells, it caused the body to release too many immune-boosting proteins called cytokines. This led to a lot of immune cells moving into the lungs, destroying lung tissue, and filling the lungs with blood and mucus. This made it very hard for people to breathe and could lead to suffocation.
The name "Spanish" flu came about because Spain was the only country in Europe where newspapers were reporting on the outbreak. Other countries kept the news quiet to protect spirits during World War I (1914–1918).
1976 Swine Flu Outbreak
In 1976, a new swine H1N1 flu virus caused serious breathing problems in 13 soldiers at Fort Dix, New Jersey. One soldier died. The virus was only found for a short time and didn't spread beyond Fort Dix. It's still not known how the outbreak started, and no one found any link to pigs.
The 1977 Russian Flu
The 1977 Russian flu pandemic was caused by an H1N1 strain. It mostly affected children and young adults under 23. This was because a similar flu strain had been around from 1947 to 1957, so most older adults already had some protection. The virus was later included in the 1978–79 influenza vaccine.
The 2009 H1N1 Pandemic
The 2009 flu pandemic was caused by a new H1N1 virus. This virus was a mix of genetic material from four different flu viruses: North American swine flu, North American bird flu, human flu, and swine flu from Asia and Europe. This unusual mix happened through a process called reassortment, where different flu viruses swap genetic parts.
In April 2009, a flu-like illness started in Mexico and then spread to the United States. The CDC quickly shared the genetic information of the new H1N1 virus. By April 24, it was clear that the outbreaks in Mexico and the US were connected. The WHO then issued a health warning.
The disease spread very quickly. On June 11, 2009, the WHO declared an H1N1 pandemic. This was the first global flu pandemic since the 1968 Hong Kong flu. On October 25, 2009, U.S. President Barack Obama declared H1N1 a national emergency.
The H1N1 flu could sometimes cause serious problems like blood clots in the lungs. This was a leading cause of death in this pandemic.
By March 21, 2010, the WHO reported that 213 countries had confirmed cases of the 2009 H1N1 flu, with at least 16,931 deaths. By May 30, 2010, over 214 countries reported more than 18,138 deaths. Studies showed that pregnant people were at higher risk of severe illness.
In August 2011, scientists found that northern sea otters off the coast of Washington state were infected with the same H1N1 virus from the 2009 pandemic. This suggested that sea otters might be a new animal that can carry the flu virus.
H1N1 outbreaks continued in different parts of the world in the following years:
- 2012 India Outbreak: Over 300 infections and 20 deaths were reported.
- 2015 India Outbreak: By mid-March, 31,974 cases and 1,895 deaths were reported.
- 2017 Maldives Outbreak: 185 out of 501 tested people were positive, with four deaths. Schools were closed for a week.
- 2017 Myanmar Outbreak: 30 confirmed cases and six deaths by late July. Myanmar asked the WHO for help.
- 2017–18 Pakistan Outbreak: Mostly in Multan, with 42 deaths. Cases also in Gujranwala and Lahore.
- 2019 Malta Outbreak: The main hospital was overcrowded with over 30 cases in mid-January.
- 2019 Morocco Outbreak: Nine confirmed deaths in January.
- 2019 Iran Outbreak: 56 deaths and 4,000 hospitalizations in November.
The G4 Virus
The G4 virus, also known as "G4 swine flu virus," is a type of H1N1 swine influenza virus found in China. It mainly affects pigs, but there's some evidence it can infect people too.
Scientists have been watching this virus since 2011. The Chinese CDC has a program to monitor flu viruses in pigs. They found 13 cases of A(H1N1) in humans, and three of those were the G4 type.
A study looked at almost 30,000 pigs between 2011 and 2018. It suggested that the G4 variant had become the main strain in pigs since 2016. However, the Chinese Ministry of Agriculture disagreed, saying the sample size was too small. They also noted that infected workers didn't show flu symptoms.
Health officials, including the US Centers for Disease Control and Prevention (CDC) and the European Centre for Disease Prevention and Control (ECDC), say that the G4 virus should be watched closely. This is because it has the potential to cause a pandemic, like other flu viruses. They emphasize that developing human vaccines is important for preparing for such a possibility.
As of July 2020, there were no reported cases of the G4 virus outside China. Scientists agree it needs close monitoring, especially among people who work with pigs. However, since it hasn't shown the ability to spread easily from person to person yet, it's not an immediate cause for alarm.
H1N1 and Pregnancy
Pregnant people who get the H1N1 infection are at a higher risk of getting very sick. This is because their bodies go through many changes during pregnancy. For this reason, the Centers for Disease Control and Prevention suggests that pregnant people get vaccinated to prevent the flu.
It's important to talk to a doctor about vaccination. People who have had a severe allergic reaction to a flu shot should not get it. Also, if someone is very sick with or without a fever, they should wait until they feel better before getting vaccinated.
Treating H1N1 Infection
If someone gets the flu, especially if they are pregnant, they should contact their doctor right away. Doctors can prescribe special antiviral medicines to treat the flu.
Two common antiviral medicines are Oseltamivir (brand name Tamiflu) and zanamivir (Relenza). These work best if taken within two days of feeling sick.
Scientists regularly test flu viruses to see if they are resistant to these medicines. For example, after the 2009 H1N1 pandemic, only a small number of H1N1 virus samples showed resistance to oseltamivir, and none were resistant to zanamivir.
