H1N1 (Swine flu)

H1N1 (Swine flu)

• Pathogen & Transmission

Novel swine-origin influenza A(H1N1) is a brand new virus created by a modification of original swine flu (A(H1N1)). It was found in the city of San Diego, California, USA for the first time. It was found in the clinical specimen of 10 years old child who were hospitalized due to the fever, cough and vomit.

The virus that causes influenza is called influenza virus. Due to its genetic identity, it is classified as A type and B type. A type virus contains proteins called hemagglutinin and neuraminidase. They are types of surface antigens. Each A type influenza virus has respectively one type of hemagglutinin out of H1 to H16[1] and one type of neuraminidase out of N1 to N9[2]. Hemagglutinin contributes to a role when the virus attach itself to the cell (have 15 types) and Neuraminidase has a role of separating infected cell and the virus itself (have 9 types). Influenza viruses vary due to the type of hemagglutinin and neuraminidase.

Influenza virus A(H1N1) is an A type of influenza virus containing hemagglutinin H1 and neuraminidase N1. In the mid-term of April in 2009, the first patient was found in U.S and consequently few other patients who were infected by H1N1 are also found in Mexico. Then it was spread world widely, thus WHO declared as a pandemic in 11th of July in 2009.

Influenza virus has a special characteristic, which is antigenic modification. They are classified as antigenic drift and antigenic shift based on the size of modification. The A type influenza virus shows a various modification due to different types and modifications of hemagglutinin and neuraminidase. It was studied that this new virus that outbreak is genetically different to the original A(H1N1) virus and re named as novel swine-origin influenza A(H1N1). An antigenic shift is only possible for A type influenza virus and the type of HA and NA of the original virus change into complete new NA and HA. The hemagglutinin antigen is especially important, because it is possible to prevent an infection based on the existence of an antibody for that HA.

In general, Influenza viruses cause an infection in one species. However, in one host cell, more than two influenza viruses invade occasionally and genetically mix together resulting a modification (antigenic shift). Specialists are assuming that new A(H1N1), novel swine-origin influenza was modified in similar process like this. New influenza viruses cause a pandemic and this kind of pandemic results a large numbers of casualties. In the past, the cases that got infected by a flu originated from pig between people were also reported often, however it was an epidemic. However, pandemic in 2009 resulted 214 countries under an infection and approximately 18,500 deaths.

It was originally called swine flu because in the past, the people who caught swine flu had a direct contact with pigs. Swine is a bad word for pig. The swine flu spreads in similar way as the seasonal flu. It is spread respiratory. For instance, it is spread by coughing, or sneezing. Specifically, they spray tiny drops of the virus into the air. If you come in contact with these drops, you are opened to catch H1N1 flu.[3][4]

---

[1] (Type of surface antigen)

[2] (Type of surface antigen)

[3]신종 인플루엔자 A(H1N1)". Terms.naver.com. N.p., 2017. Web. 24 Mar. 2017.

[4]신종 인플루엔자는 무슨 뜻인가요? 왜 신종이 붙나요?". Terms.naver.com. N.p., 2017. Web. 24 Mar. 2017.

• Monitoring and patterns of infection

The large-scale movements of a herd of swine from the South to the West spreads the H1N1 virus.  The long distance movements of swine should be noted when monitoring the patterns of infection. The movements of swine evolves and the spatial dissemination of the swine flu may allow us to develop a future strategies for monitoring the disease.

• Symptoms and causes of death

The incubation time of H1N1 varies from one to four days. The symptoms of H1N1 are mostly fever, coughing, fatigue, and headache, which are very similar to influenza infections. However, patients may also suffer from vomiting, nausea, diarrhoea, muscle pains, and red eyes. The symptoms last about one to two weeks. Some severe patients may suffer from a malfunction of their respiratory system, leading to being assisted when breathing. H1N1 and influenza are very similar in the way of causing death. A toxic virus enters the respiratory tract. The immune system responds with an influx of white blood cells, where the influx blocking the respiratory tract, and ultimately, harming the lungs. The immune system also releases cytokine; the cytokine activity in the respiratory tract cause inflammation. Therefore, the symptoms are similar to influenza. Pneumonia may occur due to the infection, which is the main cause of death. In some cases, the damage in the respiratory tissue allows a bacterial infection to occur, which is another cause of death.

• Fever
• Cough
• Sore throat
• Runny or stuffy nose
• Watery, red eyes
• Body aches
• Headache
• Fatigue
• Diarrhea
• Nausea and vomiting

• Prevention & Treatment

There are various ways in which we can prevent ourselves from getting infected. First of all, we can acclimatize to the habit of washing our hands thoroughly and frequently. Swine flu is one of the many viruses which can spread by a contact. Most of the people are unaware of the dangers which our hands can transmit from person to person. To prevent this danger, we can rinse the virus off our hands by using soaps and washing chemicals; but yet we can not kill it. Also, we can contain coughs and sneezes by covering the mouth. To avoid contaminating our hands, we can choose to cough into a tissue. Moreover, if the patient seems to have flu like illness such as fever,cough, they should be isolated immediately,due to its high contagiosity. The contagious period for swine flu begins one day before symptoms develop in adult and it lasts about 5 - 7 days. Since it starts to spread before we are able to catch the symptoms,it is very crucial to exclude the sickly looking people as soon as possible although we are unsure about the exact reason behind it. Vaccination is the best way to prevent or reduce the chances of becoming infected.

As a treatment,vaccine is available as an injection or a nasal spray. But, nasal spray is not recommended for people who are older than 50 or younger than 2. The usage of Amantadine is one of the methods to treat swine flu. It is the organic compound which is approved for use as an antiviral drug. However, 2009 pandemic flu samples tested showed resistance. Therefore, it is no longer being used. Zanamivir is better drug to treat and prevent this. It is a neuraminidase inhibitor which was approved in the US in 1999 only for use as a treatment for influenza. It was administered to 411 patients(70 had H1F1).

• Notable historical outbreaks

H1N1 was first discovered in the state of Veracruz, Mexico. Right after the outbreak, the mexican government closed Mexico city to prevent the spread of the virus. But, unfortunately, the virus continued to spread globally resulting some area to get overwhelmed by infected people.

In 2009, swine flu was first described. This is the geographical distribution of the swine flu in 2009. If we look at the map, Africa is barely invaded. The big continents such as China, Russia, USA, Canada, Australia are invaded more.

• Interesting facts

1. Swine flu viruses may mutate so that they are easily transmissible.
2. The incubation period for the disease is about one to four days.
3. Two antiviral agents “zanamivir” and “oseltamivir” have been reported to help prevent or reduce the effects of swine flu.
4. One of the unusual characteristic of the swine flu is that it does not infect adults older than 60.
5. Even with the healthy people, a small percentage can develop pneumonia.

• Citations (hyperlinks) and bibliography (with URL)

http://www.mayoclinic.org/diseases-conditions/swine-flu/basics/prevention/con-20034916

http://www.medicinenet.com/swine_flu/article.htm

https://en.wikipedia.org/wiki/Amantadine

http://www.mayoclinic.org/diseases-conditions/swine-flu/basics/symptoms/con-20034916 https://academic.oup.com/cid/article/48/7/996/327879/Comparison-of-the-Effectiveness-of-Zanamivir-and

Eugene Yang, Sally Choi, Bradley Min