Swine Flu Detected in 2 Children; Human-to-Human Spread Possible

April 22, 2009 — H1N1 swine influenza A infection has been reported in 2 children living in southern California. No direct contact with swine was reported in either case, suggesting that the virus may have spread directly among humans.

The cases were reported online April 21 in a special dispatch of the Morbidity and Mortality Weekly Report (MMWR), issued by the US Centers for Disease Control and Prevention (CDC). The swine viruses detected contain combinations of DNA segments not previously observed in influenza virus, and the seasonal influenza vaccine H1N1 strain is unlikely to provide protection, according to the report. The viruses also demonstrated antiviral resistance to amantadine and rimantadine.

According to CDC spokesperson Tom Skinner, it is not yet known whether this swine flu is susceptible to zanamivir (Relenza, GlaxoSmithKline) or oseltamivir (Tamiflu, Roche). “Results of testing should be available within a day or 2,” he told Medscape Infectious Diseases in a telephone interview. He added that interim recommendations from the CDC suggest that clinicians should use either oseltamivir or zanamivir if they suspect that a patient has swine flu.

Two Patients Infected

The MMWR report describes 2 patients with swine influenza. One patient was a 10-year-old boy living in San Diego County, California, who traveled by airplane from San Diego to Dallas while sick with flu-like symptoms. These symptoms resolved uneventfully within a week. The patient, who continues to reside in Dallas, tested positive for influ¬enza A virus, but the test was negative for human influenza subtypes H1N1, H3N2, and H5N1. The CDC subsequently determined that the virus was swine influenza A (H1N1).

The second patient was a 9-year-old girl who lives in Imperial County, California, which is adjacent to San Diego County. She had a cough and fever, was treated with amoxicillin/clavulanate potassium and an antihistamine, and made a full recovery.

“Two is a very small sample size, but I think it is unlikely that this swine flu is associated with severe flu symptoms,” Stephen Munday, MD, MPH, the public health officer for Imperial County, told Medscape Infectious Diseases. “Both of these cases would have completely recovered without medical intervention, and at least so far, there seems to be no propensity for severe influenza.”

Dr. Munday added that of the 50 severe cases of pediatric influenza in California this flu season that would have been thoroughly evaluated because of their severity, no cases of swine influenza were detected.

“Other cases of swine flu may have occurred but remained undetected because they were mild and/or were not evaluated,” he said and added that several close contacts of the patients with influenza-like symptoms are currently being evaluated to determine any relationship with the case patient viruses.

Need for Influenza Surveillance

These cases highlight the need for proper testing for suspected influenza virus, “not just in California, but around the country,” Dr. Munday said.

The MMWR report advises clinicians who suspect swine influenza virus infection in humans to obtain a “nasopharyngeal swab from the patient, place the swab in a viral transport medium, and contact their state or local health department to facilitate transport and timely diagnosis at a state public health laboratory.”

The CDC also requests that state public health laboratories send all influenza A specimens that cannot be subtyped to the CDC, Influenza Division, Virus Surveillance and Diagnostics Branch Laboratory.

Swine Flu on the Rise

According to the editorial note in the MMWR report, a total of 14 cases of swine influenza in humans, including the 2 current cases, have been reported since December 2005. This number represents an increase compared with previous years. This may be partly a result of an increase in influenza testing capabilities in public health labo¬ratories, although “genetic changes in swine influenza viruses and other factors also might be a factor,” the authors note.

“The lack of known exposure to pigs in the two cases described in this report increases the possibility that human-to-human transmission of this new influenza virus has occurred,” they add.

According to the CDC’s Tom Skinner, with the increased level of influenza surveillance now taking place in Southern California, “it would not be a surprise to detect more suspected cases that warrant further investigation. As the CDC learns more about these cases we will update information regarding these cases,” he said.

Morb Mortal Wkly Rep. Published online April 21, 2009.


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