In the spring of 2009, a new influenza A (H1N1) virus emerged, causing an illness later known as Influenza A. It was first detected in the United States and spread rapidly around the world. This novel H1N1 virus contained a unique combination of influenza genes not previously identified in animals or people. The new virus outbreak was named H1N1pdm09.
From April 12, 2009 to April 10, 2010, the Centers for Infectious Disease Control estimated that there were 60.8 million cases globally, 274,304 hospitalizations, and 12,469 deaths in the United States.
Since the 2009 H1N1 pandemic, the virus has circulated seasonally causing a significant number of cases, hospitalizations and deaths. We review, in six questions, the most important data on Influenza A.
1. What is influenza A?
It is a disease caused by a type A influenza virus that affects pigs and, exceptionally, is transmitted to their keepers.
2. What is special about this virus?
It was triggered by a strain of the virus that is a hybrid between human, swine, and avian influenza viruses, and can be spread from human to human. The World Organization for Animal Health (OIE) considered the name ‘swine flu’ inappropriate – since it also has avian and human components. The official name of this disease is Influenza A, but it is also known as the North American Flu.
3. What are the symptoms?
Fever, cough, sneeze, ocular congestion, sore throat, joint pain, headache, and general malaise. In some cases it is also accompanied by diarrhea and vomiting. If respiratory failure occurs or pneumonia is triggered it can be fatal. This is also the case with the common human flu, which claims thousands of lives each year; and with the SARS-CoV-2 coronavirus, which causes the COVID-19 disease, and which has spread across the planet causing a global pandemic.
4. Is there a vaccine and / or treatment?
Since the (H1N1) pdm09 virus was very different from the already circulating H1N1 viruses, vaccination against seasonal influenza offered little cross-protection. Although a monovalent (H1N1) pdm09 vaccine was manufactured, it was not available in large quantities until after the peak of illness.
In addition, it was found that the progression of the disease could be slowed with oseltamivir and zanamivir.
5. What scope did it have?
The new virus appeared in Mexico and quickly spread to the southern United States. Other countries reported infections in a short time, such as Canada, Spain, Israel, Great Britain, New Zealand, Italy, Germany, France and El Salvador. Estimates of pandemic influenza mortality range around 0.03% of the world’s population .
6. When did the pandemic end?
On August 10, 2010, the WHO announced the end of the H1N1 influenza pandemic. Although it did not have such devastating effects as the pandemic known as the ‘Spanish flu’ of 1918, nor the COVID-19 pandemic that we are currently experiencing.
However, the virus continues to circulate, causing some serious but anecdotal cases; mainly affecting children and young and middle-aged adults.
