Recently a new strain of influenza has led to an endemic in humans and in swine in greater parts of Mexico and the rest of the globe. The World Health Organization raised its global alert level on the spreading swine flu virus, but stopped short of declaring a global emergency.

Swine influenza, also known as swine flu, refers to influenza caused by any virus of the family Orthomyxoviridae, that is endemic to pig populations.

The CDC reports that the symptoms and transmission of the swine flu from human to human is much like that of seasonal flu. Common symptoms include fever, lethargy, lack of appetite, coughing, runny nose, sore throat, nausea, vomiting, and diarrhea have been reported.

The influenza is not uncommon; in 1976, an army recruit died at Fort Dix a day after comments of feeling tired and weak. After that four other fellow recruits were diagnosed and hospitalized. Earlier history dates back to the 1918 flu pandemic, in which 500,000 American died, a total of 20 million worldwide.

It is believed to be spread between humans through coughing or sneezing of infected people and touching something with the virus on it and then touching their own nose or mouth. Swine flu cannot be spread by pork products, since the virus is not transmitted through food. The swine flu in humans is most contagious during the first five days of the illness although some people, most commonly children, can remain contagious for up to ten days.

Theories for the virus are that Asian and European strains traveled to Mexico in migratory birds or in people, then combined with North American strains in Mexican pig factory farms before jumping over to farm workers, but the origins of this new strain still remain unknown.

The suspected number of deaths rose to 149 in Mexico, the epicenter of the outbreak with nearly 2,000 people believed to be infected. Civilians can be seen wearing face masks in infected areas as a precaution to prevent an influenza spread.

In the US, 40 cases were reported in states of Ohio, Kansas, New York, Texas, and California, none fatal.

President Barack Obama smoothed over the issue by reassuring Americans.

This is, obviously, a cause for concern and requires a heightened state of alert,” Obama said. “But, it’s not a cause for alarm.”