Humans and pigs share enough biological attributes that some diseases can move back and forth between the two different species. The swine flu, swine A)H1N1 is one such illness.
Influenza doesn't bother pigs much. In humans, it can range from a mild though lengthy illness to one that can produce large numbers of fatalities. The current swine flu is a bit mysterious because it seems to do a little of both.
Swine A(H1N1) was first detected in samples submitted to Canadian Public Health labs by the Mexican government. Shortly after, the United States Centers for Disease Control confirmed its existence. Mexico was undergoing a rapid and fast moving outbreak of Influenza Like Illness - ILI, and the Mexican Public Health officials were alarmed.
The genome for this variety of influenza appeared to be unique. Neither the Canadians nor the CDC labs had ever seen it before.
The media frenzy and warnings from a number of public officials worldwide caused a great deal of concern and some panic. Was this the expected influenza pandemic that everyone has been anticipating?
The Mexican outbreak was of little help. Large numbers of people were hospitalized, over 2,000 at last count, and deaths in that population numbered in the hundreds. These cases were all characterized as ILIs, though many in the media called them swine flu. Testing was slow and most of the ILI cases were not tested. Rumors ran wild.
As the number of cases increased in the United States, the picture became clearer. This swine flu produced a mild infection that lasted ten days or so. Symptoms resembled seasonal flu, upper respiratory, fever, cough. Gastric symptoms were more common in adults with swine flu than with seasonal flu, where vomiting or diarrhea are mostly found in children.
Very early in the outbreak in the United States, it became clear that human to human transmission was occurring. The first cases discovered all had histories of travel to Mexico in the two weeks prior to their illness. first at the St. Francis Prep outbreak in Queens, N.Y. and later across the country, the illness was found in people who had not gone to Mexico but who had contact with those who were ill.
The World Health Organization raised the influenza pandemic alert status to 5, because human to human transmission was found in different countries. That alert level advised public health authorities worldwide to prepare for a possible pandemic.
One of the interesting aspects of this outbreak has been the age groups affected. Normally, with seasonal influenza, young children and the elderly are most at risk. This illness seems, with limited data, to affect people under fifty, and especially those under 30 the most. The outbreak clusters at St. Francis Prep, the Newberry Academy, the University of Delaware and aboard the USS Dubuque all suggest that this influenza variant is unique in that way. That is cause for concern because it is unusual.
Nearly every state health lab in the U.S. is now certified to test for swine flu. The number of cases is climbing and will do so as the backlog of tests are performed. Not all ILIs are swine flu or even influenza. The New York State lab has found that 69% of its samples test negative for swine flu and for seasonal flu. Two thirds of the influenza cases are testing as seasonal with the remainder testing as swine flu.
While the swine flu in humans appears to be mild at this point, public health officials remind us that this is the end of the influenza season in the Northern Hemisphere. The situation may be very different as the new seasonal influenza outbreak begins in the fall of 2009. Pandemic influenza appears in waves, and if swine flu is to become a pandemic, then fall will see the proof.