Spain reports possible person-to-person swine flu case

Over the weekend, Spanish health officials told the World Health Organization about a suspected human swine flu infection that may have spread between people, ABC News reported. The patient had not had direct contact with pigs, and the WHO's influenza reference laboratory in Britain is running additional tests to confirm the diagnosis.

Health officials said the general public faces low risk, but public health experts told ABC News the case may put people who work in public health or live near the detection site on alert; broad worry is not yet warranted.

Dr. Meghan Davis, an associate professor at the Johns Hopkins Bloomberg School of Public Health who studies environmental health and engineering, said sporadic swine flu cases appear globally during any flu season. She advised people in the immediate area to pay close attention to directives from public health authorities, while people at a distance should stay aware of health messaging for further guidance.

Dean Blumberg, chief of pediatric infectious diseases at UC Davis Health, said most human infections with swine-origin influenza viruses occur in people who work closely with pigs or in the pork industry, and most cases spread directly from animals to people; very few involve human-to-human transmission.

The Centers for Disease Control and Prevention describes swine flu as a respiratory disease commonly found in pigs and caused by influenza type A viruses. Humans are not typically infected, but occasional spillover infections occur. In 2009, an H1N1 influenza virus pandemic linked to bird, swine and human flu viruses led to about 60.8 million U.S. cases, 274,304 hospital stays and 12,469 deaths, according to CDC data cited by ABC News.

Most human cases are mild and cause symptoms resembling seasonal influenza, including fever, tiredness, cough, runny nose, sore throat, sneezing, nausea, vomiting and diarrhea, the CDC says. Some patients have had serious illness resulting in hospitalization and death.

Davis told ABC News she sees the Spain case as a serious public health concern but not a major worry for the general public right now. The possibility of human-to-human transmission worries public health professionals because it could signal that the virus is adapting, she said. Blumberg agreed there is no need for major concern yet, but said the case signals a need for closer monitoring and further characterization of the strain to see whether it transmits more easily between people. He also said local studies could look for asymptomatic infections to determine whether there has been more widespread circulation.

The case remains unconfirmed pending testing. The ABC News report cannot establish whether this virus strain has acquired the ability to transmit efficiently among humans, and it does not imply that a broader outbreak is under way.