Swine Flu Outbreak

The United States has seven confirmed cases of Swine Influenza A/H1N1, five in California and two in Texas, and nine suspect cases.  All of the seven confirmed cases had mild Influenza-Like Illness (ILI).  No deaths have been reported. 

 

Mexico reports three separate event locations – Mexicali, San Luis Potosi, and the Federal District of Mexico.  The government of Mexico began surveillance of ILI March 18, 2009.  Since then, 854 cases of pneumonia have been reported in Mexico City, with 59 deaths.  San Luis Potosi, in central Mexico, reports 24 cases of ILI, with three deaths.  Mexicali, near the border with the United States, has had four cases of ILI, with no deaths.  The majority of these cases have been in healthy young adults.

 

Of the Mexican cases, 18 are confirmed Swine Influenza A/H1N1.  Twelve of the 18 are identical to the Swine Influenza A/H1N1 viruses isolated from the patients with confirmed cases in California.  Swine flu viruses do not normally infect humans.  However, sporadic human infections have occurred in persons with direct exposure to pigs and in health care workers caring for persons with swine flu.  The Centers for Disease Control and Prevention (CDC) report 12 cases of human infection with swine flu between December 2005 and February 2009. 

 

The Swine Influenza A/H1N1 viruses isolated in this outbreak appear to be a strain not previously detected in pigs or humans, although these reports are preliminary.  Because there is reported spread of an animal virus in humans, and because of the geographical spread of multiple community outbreaks, these events are of concern, and the CDC is working to further characterize the viruses and provide guidance for treatment and prevention.

 

The symptoms of swine flu in humans are expected to be similar to the symptoms of seasonal human influenza, and include fever, malaise, lack of appetite, and coughing.  Some patients with the swine flu have reported runny nose, sore throat, nausea, vomiting, and diarrhea.  The H1N1 swine flu viruses are antigenically different from human H1N1 viruses, and vaccines for the human seasonal flu are not expected to provide protection from the swine flu viruses. 

 

To diagnose swine influenza A infection, a respiratory specimen must be collected and sent to the CDC for testing.  The specimen must be collected in the first 3-4 days of the illness, when the virus is shedding.  Testing may require an additional 3-4 days.  The CDC has not yet made recommendations for treating patients with an antiviral medication while the testing is pending, although these recommendations are expected later today. 

 

There are four different antiviral medications available for use in the United States for influenza:  amantadine, rimantadine, oseltamivir and zanamivir.  The most recent swine influenza viruses isolated from humans are resistant to amantadine and rimantadine.  At this time, the CDC recommends the use of oseltamivir or zanamivir for the treatment of infection with swine influenza viruses. 

 

The outbreak of “swine flu” in North America is a growing cause of concern in the World Health Organization (WHO) and in scientists worldwide concerned with pandemic prevention.  Recent improvements in pandemic preparedness may be tested by this emerging threat.