International Notes Update: Influenza Activity -- Worldwide, 1988-89

During the 1988-89 influenza season (October 1, 1988, to September 30, 1989), all three influenza virus types (influenza type A(H1N1), A(H3N2), and B) were associated with influenza-like illnesses worldwide. This report summarizes reported worldwide influenza activity since April 1989.

Oceania. In the southern hemisphere, peak influenza activity typically occurs between June and September. In Australia and New Zealand, outbreaks intensified in August; although influenza B was the predominant virus, both influenza A(H1N1) and A(H3N2) were also isolated. The first isolates of B/Yamagata/16/88-like viruses outside Asia were reported from Australia. From July to October, Papua New Guinea reported major epidemic influenza activity involving both influenza A(H3N2) and influenza B.

Asia. Sporadic influenza activity occurred in Hong Kong during July and August; most isolates were influenza A(H3N2). Since April, Japan has reported 13 influenza A(H3N2) and 24 influenza B isolates. In Thailand, peak influenza activity occurred in July; influenza A(H3N2) (22 isolates) and influenza B (21 isolates) were equally distributed with few influenza A(H1N1) viruses (four isolates). Since April, only sporadic cases of influenza-like illnesses have occurred in southern China. CDC, in collaboration with the Institute of Virology, Chinese Academy of Preventive Medicine, has analyzed 102 isolates received from May to September; 64% were influenza A(H3N2), 20% were influenza A(H1N1), and 16% were influenza B.

South America. During July and August, outbreaks of influenza-like illnesses occurred in Chile, and a few influenza A(H1N1) viruses were isolated (1).

Europe, Canada, and the United States. Low levels of influenza activity were reported in the northern hemisphere during the summer months. One case of influenza A(H3N2) occurred in England, in Canada, and the in United States in September. The U.S. case-patient was a 20-year-old student from Wisconsin who was returning from West Africa when she became ill.

Active surveillance for influenza in the United States began on October 1. Although influenza-like illnesses have been reported since then, no cases were confirmed as influenza by viral isolation until November. From November 16 through November 20, the World Health Organization (WHO) collaborating laboratories confirmed influenza A(H3N2) in a 25-year-old Arizona woman, a 46-year-old Montana man, a 41-year-old Hawaii man, and a 42-year-old Washington man. Further characterization of these isolates is pending at CDC.

Characterization of influenza virus isolates. During the 1988-89 worldwide influenza season, greater than 600 isolates were characterized by the WHO Collaborating Centre for Influenza; 46% were influenza B viruses, 30% were influenza A(H3N2), and 24% were influenza A(H1N1). The predominant A(H3N2) strains were A/Shanghai/11/87-like viruses, and the predominant A(H1N1) strains were A/Singapore/6/86- or A/Taiwan/1/86-like viruses. Influenza B isolates outside Asia have been predominantly B/Victoria/2/87-like; in Asia both B/Yamagata/16/88- and B/Victoria/2/87-like viruses have been characterized. Reported by: SJ Englender, MD, State Epidemiologist, Arizona Dept of Health Svcs. K Welch, MD, Lahaina; EW Pon, MD, State Epidemiologist, Hawaii Dept of Health. JK Gedrose, MN, State Epidemiologist, Montana State Dept of Health and Environmental Sciences. JM Kobayashi, MD, State Epidemiologist, Washington Dept of Health and Social Svcs. JP Davis, MD, State Epidemiologist, Wisconsin Dept of Health and Social Svcs. Participating state and territorial health depts. WHO Collaborating Laboratories. Sentinel Physicians of the American Academy of Family Physicians. Influenza Br and Epidemiology Office, Div of Viral and Rickettsial Diseases, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: Reports of confirmed influenza illnesses in the United States during November highlight the need for prompt vaccination of high-risk persons before widespread influenza activity occurs. The most important measure for reducing the impact of influenza is yearly vaccination of persons at high risk for influenza complications and health- and service-care providers to persons at high risk (2). Persons at high risk for complications include all persons greater than or equal to 65 years of age; persons with chronic pulmonary or cardiovascular disorders (including children with asthma); residents of nursing homes and other chronic-care facilities; persons requiring medical follow-up in the past year for chronic metabolic disorders, renal dysfunction, hemoglobinopathies, or immunosuppression; and children and teenagers receiving long-term aspirin therapy. In addition, vaccination is recommended for persons (including health-care workers) attending to high-risk persons or living in a household with a person at high risk for influenza-related complications. Although the preferred time of vaccination is late autumn, vaccine can be given throughout the winter. Efforts should be made to vaccinate high-risk persons and care providers until influenza activity has peaked in the community. The hemagglutinin antigenic components of the 1989-90 influenza vaccine include A/Taiwan/1/86-like (H1N1), A/Shanghai/11/87-like (H3N2), and B/Yamagata/16/88-like viruses.

Amantadine can be a useful adjunct to vaccination when influenza A is present in a community (3). Viral throat or nasopharyngeal cultures from patients presenting with influenza-like illness should be done to monitor possible introduction of influenza into the community, determine the infecting strain, and guide in use of amantadine for prophylaxis. Health-care providers are urged to report influenza-like outbreaks to local and state health departments.

References

1. WHO. Influenza. Wkly Epidemiol Rec 1989;64:328.

2. ACIP. Prevention and control of influenza: part 1, vaccines. MMWR 1989;38:297-8,303-11.

3. ACIP. Prevention and control of influenza. MMWR 1988;37:361-4,369-73.

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