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Delaware Health Alert Network #54

November 14, 2003 1:55 pm

Health Advisory

The Delaware Division of Public Health (DPH) reports the first diagnosed case of influenza during the 2003-2004 season. DPH encourages the submission of specimens from suspect influenza cases for culture and subtyping.

This advisory contains the following:

  • Case Information
  • Surveillance for Influenza
  • Clinical Symptoms
  • Prevention and Treatment
  • Role of Laboratory Diagnosis and Availability of Testing through DPH
  • Who should be Vaccinated
  • Further Information

Case Information

The reported case is a six-year-old Sussex County child who was diagnosed with influenza B using a rapid influenza test. The positive rapid test was not confirmed by culture.

Surveillance for Influenza

While rapid tests are not as sensitive and specific as a culture (see below), this finding represents early evidence that influenza may be circulating in Delaware. DPH conducts active surveillance to identify increases in influenza-like illness and also maintains hospital-based surveillance for trends in respiratory, neurological, gastrointestinal and other syndromes. To date this influenza season, these surveillance systems have not identified increases in respiratory illness.

According to the Centers for Disease Control and Prevention (CDC), from October 25 to November 1, 2003, 45 specimens tested by U.S. World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories were positive for influenza. Four influenza A (H3N2) and 41 unsubtyped influenza A viruses were identified.

Clinical Symptoms

  • Influenza viruses are spread from person to person primarily through the coughing and sneezing of infected persons.
  • The incubation period for influenza is 1--4 days, with an average of 2 days.
  • Adults typically are infectious from the day before symptoms begin through approximately 5 days after illness onset.
  • Children can be infectious for >10 days, and young children can shed virus for <6 days before their illness onset.
  • Severely immunocompromised persons can shed virus for weeks or months.
  • Uncomplicated influenza illness is characterized by the abrupt onset of constitutional and respiratory signs and symptoms (e.g., fever, myalgia, headache, severe malaise, nonproductive cough, sore throat, and rhinitis).
  • Among children, otitis media, nausea, and vomiting are also commonly reported with influenza illness.
  • Respiratory illness caused by influenza is difficult to distinguish from illness caused by other respiratory pathogens on the basis of symptoms alone.
  • Influenza illness typically resolves after a limited number of days for the majority of persons, although cough and malaise can persist for >2 weeks.
  • Among certain persons, influenza can exacerbate underlying medical conditions (e.g., pulmonary or cardiac disease), lead to secondary bacterial pneumonia or primary influenza viral pneumonia or occur as part of a coinfection with other viral or bacterial pathogens.
  • Young children with influenza infection can have initial symptoms mimicking bacterial sepsis with high fevers and <20% of children hospitalized with influenza can have febrile seizures. Influenza infection has also been associated with encephalopathy, transverse myelitis, Reye syndrome, myositis, myocarditis and pericarditis.

Prevention and Treatment

  • Vaccination: Vaccination is still effective even as influenza season progresses. Any person for whom vaccination is not contraindicated should be vaccinated if interested. Groups at risk and contraindications are included at the end of this health advisory.
  • Anti-virals: While not a substitute for vaccination, there are four antivirals active against influenza. Amantadine and rimantadine can be used to treat and prevent influenza A infections. These drugs do not work against influenza type B viruses. Zanamivir and oseltamivir can be used to treat influenza A and B infections. Oseltamivir can also be used for prevention of influenza A and B. Studies show that treatment with any of these drugs can shorten the time a person infected with influenza feels ill by approximately 1 day, if treatment is started during the first 2 days of illness
  • Personal hygiene: Influenza is transmitted by both airborne and direct methods. It may persist for hours in the environment. Prevention is aided by thorough hand washing with soap and water, proper disposal or washing of objects contaminated by an infected person's nasal or throat discharges, avoidance of hand to mucus membrane contact, and covering of cough and sneezes,

Role of Laboratory Diagnosis and Availability of Testing through DPH

Appropriate treatment of patients with respiratory illness depends on accurate and timely diagnosis. The early diagnosis of influenza can reduce the inappropriate use of antibiotics and provide the option of using antiviral therapy. However, because certain bacterial infections can produce symptoms similar to influenza, bacterial infections should be considered and appropriately treated, if suspected. In addition, bacterial infections can occur as a complication of influenza.

Diagnostic tests available for influenza include viral culture, serology, rapid antigen testing, polymerase chain reaction (PCR) and immunofluorescence. Commercial rapid diagnostic tests are available that can be used by laboratories in outpatient settings to detect influenza viruses within 30 minutes. These rapid tests differ in the types of influenza viruses they can detect and whether they can distinguish between influenza types. The specificity and, in particular, the sensitivity of rapid tests are lower than for viral culture and vary by test. Because of the lower sensitivity of the rapid tests, physicians should consider confirming negative tests with viral culture or other means.

Despite the availability of rapid diagnostic tests, collecting clinical specimens for viral culture is critical, because only culture isolates can provide specific information regarding circulating influenza subtypes and strains. This information is needed to compare current circulating influenza strains with vaccine strains, to guide decisions regarding influenza treatment and chemoprophylaxis, and to formulate vaccine for the coming year. Virus isolates also are needed to monitor the emergence of antiviral resistance and the emergence of novel influenza A subtypes that might pose a pandemic threat

The Delaware Public Health Laboratory (DPHL) offers rapid influenza testing, which will be followed by culture and subtyping, to health care providers in Delaware. Details regarding sample collection and transport can be obtained by calling DPHL at 302-653-2870. This service is provided free of charge. DPH encourages the submission of samples for influenza testing, especially early in the influenza season when information about circulating subtypes is most important.

Who Should Be Vaccinated

Groups At Risk For Complications From Influenza

  • Persons aged >50 years;
  • Residents of nursing homes and other long-term care facilities;
  • Adults and children > 6 months of age who have chronic heart or lung conditions, including asthma;
  • Adults and children > 6 months of age who need regular medical care or were hospitalized because of metabolic diseases (like diabetes), chronic kidney disease, or weakened immune systems (including immunosuppressive medications, HIV/AIDS);
  • Children and teenagers (aged 6 months to 18 years) who are on long-term aspirin therapy and therefore could develop Reye Syndrome after the flu;
  • Women who will be more than 3 months pregnant during the flu season.
  • Because young, otherwise healthy children are at increased risk for influenza-related hospitalization, influenza vaccination of healthy children aged 6-23 months is encouraged when feasible.

Persons Who Can Give Influenza To People Who Are At High Risk For Complications:

  • Doctors, nurses, and other employees in hospitals and doctors' offices, including emergency response workers;
  • Employees of nursing homes and long-term care facilities who have contact with patients or residents;
  • Employees of assisted living and other residences for people in high-risk groups; People who provide home care to those in high-risk groups;
  • Household members (including children) of people in high-risk groups.

The Following Groups Should Not Get A Flu Shot Before Talking With Their Doctor:

  • People who are have a severe allergy to hens' eggs
  • People who have had a severe reaction to a flu shot in the past
  • People who previously developed Guillain-Barré syndrome (GBS), a rare disorder of the nervous system, within 6 weeks after getting a flu shot
  • In addition, the following groups should not receive the new live, attenuated intranasal flu vaccine (FluMist):
    • Persons aged <5 years
    • Persons aged > 50 years
    • Persons with a medical condition placing them at high risk for complications from influenza (see above list)
    • Children or adolescents receiving aspirin
    • Pregnant women

Further Information

Categories of Health Alert messages:

  • Health Alert: Conveys the highest level of importance; warrants immediate action or attention.
  • Health Advisory: Provides important information for a specific incident or situation; may not require immediate action.
  • Health Update: Provides updated information regarding an incident or situation; unlikely to require immediate action.
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