The total number of confirmed cases in recent months of swine flu in the US now comes to 7, with the addition earlier this month of two infected children living in adjacent counties in southern California. None of the infected people had been in contact with pigs, said the Centers for Disease Control and Prevention (CDC).

The latest status report from the CDC, as of 3 pm EST yesterday, shows that 5 of the lab confirmed cases of swine influenza A (H1N1) virus infection are from California (in San Diego County and Imperial County) and the other 2 are from Texas (both in San Antonio). All patients have now recovered.

In the case of the two children, tests revealed they had become infected with viruses that were related genetically but contained a “unique combination of gene segments that previously has not been reported among swine or human influenza viruses in the United States or elsewhere”, said the CDC in their April 21 Morbidity and Mortality Weekly Report (MMWR).

The two strains were also resistant to amantadine and rimantadine, the usual treatment for swine flu.

Swine influenza (swine flu) is a disease that regularly affects pigs. It is caused by a type A influenza virus that does not normally infect humans, although we can catch it, mostly from being near infected pigs, although it is possible for it to spread from human to human.

Symptoms are usually similar to those of regular human seasonal influenza and include fever, lethargy, lack of appetite and coughing. These can sometimes be accompanied by a runny nose, sore throat, nausea, vomiting and diarrhea. The illness is rarely fatal.

In the past, the CDC has received reports of swine flu in humans at a rate of about one every one or two years. But from December 2005 to January 2009, there have been 12 cases (a rate of 4 a year) in 10 different states. Five cases were patients who came into direct contact with pigs, six were patients who had been near pigs, and one had unknown exposure. And then in the last two months, 5 reported cases in California.

The agency said that while it looks as if the numbers of swine flu cases in humans are starting to rise, it could just be due to better testing facilities in public health labs. However, it could also be due to genetic changes in swine flu and it is important to investigate each case to make sure that new strains are not spreading more easily among humans.

In the case of the two children, they were not exposed to pigs, and members of their family had also reported flu like symptoms around the time they were infected.

This information increases the possibility that the new strain is spreading from human to human, said the CDC, who warned that doctors treating patients with flu symptoms who either live in San Diego and Imperial counties, or have travelled there in the seven days before their symptoms emerged, or have been in contact with people who live or have travelled there, should bear in mind that they could be infected with animal flu.

Doctors treating any flu patient who may have been in contact with pigs or been near pigs such as at a fair or animal display should also take note, said the agency.

Doctors who suspect a patient has swine flu should take a nasopharyngeal swab, put it in a viral transport container, and contact their state or local health department to find out how to send it quickly to a state public health laboratory.

The CDC said state public health labs should send all influenza A specimens that they can’t subtype to the CDC Influenza Division’s Virus Surveillance and Diagnostics Branch Laboratory.

Sources: CDC.