What is the flu? How many types of flu are there? Does Cambodia's geography factor into the flu infection?
In order to better understand what the flu is, we should know what causes it and how it spreads.
The flu is a contagious respiratory illness caused by the influenza virus, which belongs to a family of orthomyxoviridae viruses. The virus infects the nose, throat, and sometimes the lungs. The flu can produce mild to critical symptoms among a variety of patients, which can lead to death in extreme cases.
It’s believed that human-to-human transmission is caused mainly by droplets made when people with the flu cough, sneeze, or talk without wearing masks or covering their mouth with tissues or their hands. Touching a surface or object which has the virus and then touching the mouth, nose, or eyes is a minor cause of the infection.
There are four types of the flu: A,B,C, and D.
- Type A commonly infects people more than animals. However, it is able to infect animals as well. Research shows that only the type A viruses can cause seasonal epidemics of diseases.
- Type B is found only in humans. Compared to type A, type B flu virus causes less severe symptoms and does not cause pandemic.
- Type C is detected less frequently and causes milder infections than Type A and Type B and also does not cause epidemics.
- Type D primarily infects cattle and is not known to cause illness to humans. However, studies show that the virus does have the potential to infect humans.
According to the Centers for Disease Control and Prevention, the symptoms of flu are commonly characterized by a sudden onset of fever, dry cough, headache, runny nose, muscle and joint pain, fatigue, and vomiting or diarrhea, which is common among children.
It is important to note that everyone with the flu presents with a fever.
The influenza viruses has caused many forms of illness across the globe, such as:
- Seasonal Flu is mainly caused by viruses type A and B. It is believed to be caused by drops in the temperature, which allows the virus to replicate at a faster rate and spread change between internal and external environment
- Swine Flu is caused by a type A virus. It caused a pandemic among pigs that lasted about 19 months in 2009. It was first found in North America. As of now, swine flu is not known to be infectious to humans.
- Bird Flu, also known as Avian Flu, is caused again by type A virus. This virus is very deadly among bird species. At the same time, it can also infect humans and other animals. Severe illnesses are caused by H5N1 and H7N9 variants, viruses for bird-to-human transmission.
- Spanish Flu was caused by a type A virus, creating a large pandemic in 1918. It was called the Spanish flu because Spain was hardest hit by the pandemic, compared to other countries to which the disease spread. Globally, it is estimated that around 50 million to 70 million people died because of the Spanish flu. Some said the number is as high as 100million, making it the deadliest pandemic in history.
- Asian Flu first occurred in Guizhou, China around late 1956 to early 1957. It killed at least 1 million people worldwide.
- Hong Kong Flu was first reported on July 13, 1968. According to the CDC, the virus killed approximately 1 million people worldwide.
Season Flu cases caused by viruses type A and B have sharply increased every year. According to the World Health Organization, there are annually one billion seasonal flu cases across the world, with one to five million critical cases and 290,000 to 650,000 cases of death due to respiratory infection.
Pasteur Institute of Cambodia states that Cambodia’s seasonal flu cases highly rise between June and December. Cases of seasonal flu in Cambodia are believed to be caused by the drop in temperature, however the Pasteur Institute was unable to confirm the cause.
Technicians at the Institute said that the average number of infected cases in Cambodia cannot be provided due to the information being contractually bound to confidentiality .
However, seasonal flu in Cambodia is generally not as severe as it is in Eastern European countries, since Cambodia is geographically located in a hot and wet tropical zone north of the equator.
Sum Chiva, a former technician of the virology department in charge of influenza disease at the Pasteur Institute, said “Cambodia is located in a hot climate zone leading to lower number of cases, compared to countries with a cold climate, which is favorable to fast growth and duplication of the virus. The seasonal flu can be killed by temperatures higher than 30 degree celsius.”
Seasonal flu in Cambodia is primarily caused by A/H1N1 pdm (H1N1 Pandemic), A/H3N2, B/Yamagata, or B/Victoria, added Chiva.
European experts advise their citizens to get an annual flu vaccine for prevention against the illness. The vaccine is also available in the Kingdom, of which many people are not aware.
Chiva suggested that Cambodians should be vaccinated against the flu in spite of the country’s hot climate.
He continued, “We should get a flu shot because the body can stimulate defenses considerably faster as soon as we become infected. People with weakened immune systems are more likely to become ill for a longer period of time without the flu vaccine injection.”
If you are unsure the flu vaccine is right for you, experts also encourage people to protect themselves from the virus with simple measures like washing hands, exercising regularly, keeping distance from flu patients, covering your mouth when you cough or sneeze, and getting adequate sleep during the flu season.