Pandemic (H1N1) 2009

Health Alert Update – July 16, 2009

This Health Alert Update addresses the changes in local health jurisdiction (LHJ) reporting requirements for pandemic (H1N1) 2009 influenzacases and outbreaks and provides guidance for clinicians. Please note the name change from novel influenza A (H1N1) in keeping with the World Health Organization’s nomenclature.

Changes in pandemic (H1N1) 2009 influenza case reporting

  • Effective immediately, LHJs are not required by CDPH to report individual outpatient cases of suspected or confirmed pandemic (H1N1) 2009 influenza. The rationale for this change in reporting is:
  • H1N1 is now widespread in communities throughout California;
  • Current outpatient data are NOT accurately or reliably reflective of disease in the general population;

-Outpatient testing is not being performed in a systematic way;

-Outpatient case data are potentially biased and non-representative of the population so are not useful data for public health purposes; and

-Reporting of outpatient cases requires significant resources at the state and local level.

  • CDPH is requesting that LHJs continue to report the following H1N1 cases:
  • Hospitalized and fatal cases using the Novel Influenza A (H1N1) Virus Case History Form (Hospitalized/Fatal Cases).

-Effective immediately, all H1N1 hospitalized and fatal case reports should be faxed to 916-440-5984.

-Please send complete hospital medical records on cases,including weight/height, if available.

  • Outbreaks of H1N1 in healthcare facilities, licensed institutions and other settings using the Preliminary Report of Communicable Disease Outbreak Form (# CDPH 9060).Please continue to fax this form to the CDPH Infectious Disease Branch at 510-620-3425.

California Department of Public Health

Pandemic (H1N1) 2009

Health Alert Update – July 16, 2009

Lessons learned: Guidance for clinicians

  • Asthmatic patients with pandemic (H1N1) 2009 infection may present with what appears to be an asthma exacerbation rather than an ILI.
  • Rapid influenza test results should not be relied upon to identify patients who are not infected with pandemic (H1N1) 2009; at this time, data using one brand suggest that ~50% of infected people may have negative rapid test results. Patients at higher risk of influenza complications who present with influenza-like illness (ILI) should receive antiviral treatment even if their rapid influenza test results are negative.
  • Studies of treatment of seasonal influenza have indicated benefit, including reductions in mortality or duration of hospitalization,even for patients whose treatment was started more than 48 hours after illness onset. Severely ill patients should receive antiviral treatment regardless of the length of time since illness onset.
  • Critically ill patients may have the potential for lower oseltamivir absorption, higher viral loads, and reduced delivery of oseltamivir to damaged tissue, therefore, treatment with higher doses of antivirals (e.g., 150 mg oseltamivir twice per day for adults) and longer courses (e.g., >5 days) may be considered in cases of severe disease or if there is evidence of clinical progression while on treatment with standard doses. No comparative studies have assessed the effectiveness of higher doses or extended treatment, but such treatment has been suggested based upon concerns about the potential for lower oseltamivir absorption, higher viral loads, and reduced delivery of oseltamivir to damaged tissue among severely ill patients. A limited number of patients have tolerated such regimens without substantial increase in adverse events.
  • Data from severe and fatal H1N1 cases in California and elsewhere indicate that obese patients (Body Mass Index >35, see: with ILI may also be at higher risk of influenza complications and should be considered for prompt antiviral treatment. Because of concerns that standard dosage recommendations may be inadequate in obese patients, as the distribution, metabolism, protein binding and clearance of many drugs may be altered and may, therefore, result in underdosing, treatment with higher doses of antivirals should be considered for hospitalized patients with a BMI>30.
  • Although a San Francisco girl was recently identified as having an oseltamivir-resistant strain of the pandemic (H1N1) 2009 virus, there is no evidence that such resistance is widespread at this time or that changes in antiviral treatment or chemoprophylaxis agents are currently indicated. The CDPH Viral and Rickettsial Diseases Laboratory is performing antiviral resistance testing on a sample of specimens and if resistance is detected additional guidance will be forthcoming.
  • Liberal use of antiviral prophylaxis for patients who are not in a category for whom it is currently recommended may increase the risk fordevelopment of antiviral resistance and is not recommended.