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Delaware Health Alert Network #261

December 22, 2011 3:21pm

Health Alert

The Division of Public Health (DPH) alerts the medical community about the emergence of two new sub-strains of influenza A with a swine origin that have occurred across five states with the potential to emerge in Delaware. To date, no documented illnesses from these influenza sub-strains have occurred in Delaware.

The Centers for Disease Control and Prevention (CDC) report that there have been no deaths but occurrences of severe illnesses, including hospitalizations, due sub-strain H3N2. This sub-strain has been identified in 11 people nationwide as follows: West Virginia 1; Indiana 2; Pennsylvania 3; Maine 2; and Iowa 3. The H3N2 sub-strain viruses are related to human influenza viruses that circulated among people in the 1990s. For that reason, it appears that children elementary school age and younger may have a higher likelihood of contracting this strain than older individuals who may have some existing partial immunity. The epidemiology of the identified H3N2 sub-strain clusters suggests person-to-person transmission.

CDC has also confirmed that influenza infection in a Minnesota child was caused by a different sub-strain that circulates in pigs: influenza A H1N2. The influenza A H1N2 sub-strain virus resembles a human strain that circulated in humans as recently as 2007. People exposed to this similar strain may have some existing partial immunity.

The increase in detected human infections due to swine-origin strains of influenza A could be occurring for a number of reasons, including improved laboratory methods, increased surveillance, or a true increase in cases. Health care providers are advised to be more vigilant for these sub-strains in patients:

  1. With influenza like illnesses (ILI) outbreaks, particularly pediatric influenza infections and outbreaks, as well as child- care and school settings, since these have been the settings in which some cases of the sub-strains have been found.
  2. With unusual or severe presentations of influenza illness especially among children.
  3. Children under 18 years of age with ILI that requires medical attention.


It is important to note that regular influenza testing does not subtype strains. Delaware Public Health Laboratory is the only laboratory in Delaware capable of sub typing these strains. The CDC laboratory confirms the test results.


Laboratory testing at CDC has confirmed that both Influenza A, H3N2 and H1N2 subtypes are susceptible to the antiviral medications Oseltamivir (Tamiflu®) and Zanamivir (Relenza®).


Influenza is reportable in Delaware. Laboratories and healthcare providers are required to report any diagnosed case to DPH, Bureau of Epidemiology (1-888-295-5156 or 1-302-744-1033) as soon as possible by telephone, fax or electronic methods. Beginning in October each year, DPH monitors the occurrence of influenza and influenza-like illnesses in hospitals, selected long term care facilities and medical clinics to track influenza trends in the state.

DPH continues to work with its influenza sentinel providers to monitor the status of influenza and conduct testing to identify strain. Sentinel providers include family and internal medicine practices, pediatricians, infectious disease physicians, child care centers, hospitals, long term care facilities, correctional institutions and educational facilities. These sentinels provide early indication of the possible presence of flu by reporting the total number of patient visits and the number of patient visits for influenza-like illness by age group. In response to these new sub-strains, DPH requested that sentinel providers submit two additional specimens each week from patients with influenza-like illness for a total of up to seven specimens per week to be tested at the Delaware Public Health Laboratory. At least two of the seven specimens should come from children under 15 years of age.

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Categories of Health Alert messages:

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  • Health Advisory: Provides important information for a specific incident or situation; may not require immediate action.
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