Epidemiologic Notes and Reports Update: Influenza Activity - - Micronesia, United States

During the summer months, outbreaks of influenza types A(H1N1) and B were reported from south pacific islands. Several sporadic cases of influenza A(H1N1) also were reported from Hawaii during that time period. In October, the first sporadic cases of influenza A(H1N1) were reported from the contiguous United States.

Micronesia. Widespread outbreak activity was reported from Micronesia for the period May through August. In the Republic of Palau, outbreaks were associated with circulation of influenza types A(H1N1) and B. Rises in titer of hemagglutination-inhibition antibody in sera collected from 101 persons in 1985 and 1986 were measured to determine the incidence of influenza virus infection. Thirty-six (51%) of 70 persons 35 years of age had influenza A(H1N1) infections compared with 4 (13%) of 31 persons greater than or equal to 35. The three type A(H1N1) viruses that were isolated were all similar to A/Taiwan/86. For influenza B virus, the serologically diagnosed infection rates were 36 (51%) and 10 (32%) in the same age groups. Thirty-four (34%) had no titer rise to either type of influenza. The incidence and characteristics of clinical illness associated with serologic evidence of infection could not be determined. Type A(H1N1) influenza was also isolated in the Republic of the Marshall Islands.

Hawaii. Two type A(H1N1) influenza virus isolates, both similar to A/Taiwan/86, have been reported from Hawaii. Serologic evidence of type A(H1N1) virus infection was detected for a third person. The patients were 20, 23, and 43 years of age, and onset of illnesses occurred in June and August.

New York. In Syracuse, influenza virus type A(H1N1), similar to A/Taiwan/86 on preliminary testing, was isolated from a 17-year-old student who was ill during mid-September.

Texas. In early to mid-October, three influenza A(H1N1) viruses were isolated in association with sporadic influenza cases in Houston. All three isolates were from children 12 years of age. Reported by M Kumangai, MO, Bureau of Health Svcs, Republic of Palau; MJ O'Leary, MD, MPH, Federated States of Micronesia; G Kobayashi, G Kunimoto, C Nevin-Woods, DO, A Tanaguchi, MD, SMD Terrell-Perica, MA, MPH, AP Liang, MD, MPH, State Epidemiologist, Hawaii Dept of Health; BE Forbes, MD, Upstate Medical Center, Syracuse, J Miller, MD, Onondaga County Health Dept, R Deibel, PhD, D Carpenter, MD, DL Morse, MD, State Epidemiologist, New York State Dept of Health; Influenza Research Center, Baylor College of Medicine, Houston, CE Alexander, MD, State Epidemiologist, Texas Dept of Health; International Health Program Office, Div of Immunization, Center for Prevention Svcs, WHO Collaborating Center for Influenza, Influenza Br, Div of Viral Diseases, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: These are the first reports of influenza virus isolates in Micronesia and the United States this season. The influenza A(H1N1) isolates obtained from both Hawaii and New York resemble A/Taiwan/86(H1N1), a new variant strain of influenza A(H1N1) (1). No influenza outbreaks have been reported in the United States. Although the initial isolates reported have all been type A(H1N1), neither the extent of influenza activity, if any, nor which influenza virus strains may circulate in the United States this season can be predicted. While it may not be appropriate to extrapolate the findings from Palau to the United States, the results of the Palau serologic survey are consistent with previous reports from Asia (1,2) indicating that contemporary strains of influenza A(H1N1) are affecting children and young adults primarily.

In addition to a trivalent inactivated influenza vaccine recommended for all high-risk persons, a supplemental vaccine containing the A/Taiwan/86 strain will be available this year in the United States. Recommendations for usage of both vaccines have been published (3,4). Production of a supplemental vaccine was possible because of early detection of the A/Taiwan/86 variant and is intended to optimize protection, particularly for high-risk persons 35 years of age. At present, the trivalent vaccine is widely available. This vaccine contains updated A(H3N2) and B strains and also an A(H1N1) component that may provide partial protection against the new A(H1N1) variants. The Food and Drug Administration released the first lots of monovalent vaccine in late October, and it should be available shortly through normal distribution channels*.

Key points to bear in mind regarding recommendations for influenza vaccine administration and treatment of influenza include:

1. High-risk persons of all ages should receive the standard trivalent vaccine according to previously published Immunization Practices Advisory Committee recommendations.

2. The Public Health Service (PHS) urges health care personnel who treat high-risk children or high-risk adults 35 years of age to provide both trivalent and supplemental A(H1N1) influenza vaccines to their patients.

3. Vaccination with the trivalent vaccine should not be delayed if the supplemental vaccine is not available at the time the trivalent vaccine would normally be given.

4. Supplemental vaccination is of potential benefit to many other groups of young persons to reduce morbidity if A(H1N1) outbreaks occur. The potential for introducing influenza to high-risk patients could be reduced by vaccinating young adult parents and siblings of high-risk children; young health care personnel who provide care for young, high-risk patients; and young employees who perform essential services in the public or private sector.

5. There is no special emphasis by the PHS to provide the supplemental vaccine to adults greater than or equal to 35 years of age. However, it may be used in this group either as an added precaution, if the physician and patient so desire, or on the basis of institutional or other local policy decisions.

6. Aspirin use during influenza, influenza-like illnesses, and chickenpox has been associated with Reye syndrome (5), a rare but serious disease. Therefore, the PHS warns that children and teenagers less than or equal to 18 years of age should not use aspirin for the treatment of these illnesses (6).

References

1. CDC. Antigenic variation of recent influenza A(H1N1) viruses. MMWR 1986;35:510-2.

2. CDC. Update: influenza activity--worldwide. MMWR 1986;35:433-4.

3. ACIP. Prevention and control of influenza. MMWR 1986;35:317-26, 331.

4. ACIP. Monovalent influenza A(H1N1) vaccine, 1986-1987. MMWR 1986;35:517-21.

5. Hurwitz ES, Barrett MJ, Bregman D, et al. Public Health Service study on Reye's syndrome and medications. Report of the pilot phase. N Engl J Med 1985;313:849-57.

6. CDC. Reye syndrome--United States, 1985. MMWR 1986;35:66-8, 73-4. *Product information about influenza vaccines can be obtained from the following manufacturers: Connaught: (800) 538-7678 (distribution to pediatricians only); Squibb: (609) 921-4071 (Squibb handles distribution of Connaught vaccine to all others); Parke-Davis: (800) 223-0432; Wyeth: (800) 321-2304.

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