As seasonal influenza wanes, be aware of H7N9
- Copyright © 2013, The American Academy of Pediatrics
The 2012-’13 seasonal influenza activity is low and continues to decline nationally. Visits to doctors for influenza-like illness are below the national baseline. But everyone must be vigilant! Continue to immunize infants and children through June 30 (i.e., date of vaccine expiration) in anticipation of further infections caused by seasonal influenza viruses this year.
Influenza viruses are unpredictable and may remain in circulation throughout the year.
A new strain of H7N9 influenza virus has been causing severe illness and death among individuals in China, but no cases of this novel influenza A virus have been reported in the United States.
Pediatricians, however, should consider the possibility of influenza A (H7N9) virus infection in children presenting with respiratory illness within 10 days of traveling to China or exposure history. While the majority of individuals infected have been adults, infection of children with this virus is possible and may result in severe respiratory illness.
Clinicians who suspect their patient may be infected with novel influenza A (H7N9) should obtain appropriate specimens and notify their local or state health department promptly. For more information, see the April 5 health advisory from the Centers for Disease Control and Prevention (CDC), http://emergency.cdc.gov/HAN/han00344.asp.
Novel strain influenza A (H7N9) virus?
Influenza A (H7N9) is a subgroup of influenza viruses that normally circulates among birds but usually does not infect humans. On April 1, the first known human cases of infection with avian influenza H7N9 viruses, very different from previously seen H7N9 viruses, were reported in China.
As of April 26, a total of 109 laboratory-confirmed human cases with influenza A (H7N9) virus have been reported in China, with several cases occurring in children. Most of these reported cases have been serious and aggressive, including 23 fatalities. Symptoms begin with high fever and cough, quickly progressing to severe pneumonia, acute respiratory distress syndrome, septic shock and multi-organ failure leading to death. There also are reports of subjects with milder illness and one possible report of a person who tested positive for the virus but did not have any symptoms.
As of April 26, there has been no evidence of ongoing human-to-human transmission. It is believed that people have been infected with the virus after contact with infected poultry because the virus has been found in birds (poultry) in China in some of the same provinces where human infections have occurred.
Preparing for possible pandemic
Chinese health authorities, the World Health Organization (WHO), the CDC and other international health organizations are investigating this potentially critical situation. Influenza viruses frequently change, creating the possibility for human-to-human transmission. Sustainable person-to-person spread is required for this to be identified as a pandemic.
Routine preparedness actions are implemented whenever a new virus with pandemic potential is identified, including:
developing a candidate virus that could be used to make vaccine if it becomes necessary (no licensed H7 vaccine is available at this time);
making and distributing test kits to detect this virus for use by public health laboratories;
creating new serological assays to study blood samples to see whether any immunity exists to this virus in the population;
conducting tests to determine H7N9 susceptibility to the licensed influenza antiviral drugs — oseltamivir and zanamivir — as well as investigational antiviral drugs; and
gathering additional information to make a more thorough public health risk assessment.
At this time, the WHO does not advise special screening at points of entry nor does it recommend any travel or trade restrictions.
Due to the severity of illness among those infected with H7N9, it is recommended that all confirmed cases, probable cases and H7N9 cases under investigation (see Interim Guidance on Case Definitions to be Used for Novel Influenza A (H7N9) Case Investigations in the United States, http://www.cdc.gov/flu/avianflu/h7n9-case-definitions.htm) receive antiviral treatment (see http://www.cdc.gov/flu/avianflu/h7n9-antiviral-treatment.htm) as early as possible. This recommendation differs from the treatment recommendations for seasonal influenza (see table below).
Laboratory testing with functional assays has indicated that H7N9 viruses are susceptible to neuraminidase inhibitors (oseltamivir and zanamivir) but resistant to adamantanes (amantadine and rimantadine). Treatment with a neuraminidase inhibitor should be initiated, even if more than 48 hours have passed after onset of illness.
Treatment should never be delayed for laboratory confirmation of seasonal influenza or H7N9 infection. Laboratory testing and initiation of antiviral treatment should occur simultaneously. (For information regarding case investigation, specimen collection and laboratory testing, see the CDC’s April 5 health advisory, http://emergency.cdc.gov/HAN/han00344.asp.
While oseltamivir can be used to treat persons of any age, zanamivir is recommended only for children ages 7 years and older. Clinicians should refer to the manufacturer’s package inserts for additional information regarding dosing, contraindications and potential adverse events. Additional guidance on the use of influenza antiviral agents, including dosage recommendations for treatment by age group can be found at www.cdc.gov/flu/professionals/antivirals/antiviral-dosage.htm.
For more details on H7N9 from the CDC, go to www.cdc.gov/flu/spotlights/h7n9-cases-update.htm?s_cid=seasonalflu-govd-003.
Dr. Bernstein is Redbook Online associate editor.