Influenza - Worldwide

From March to August 1983, influenza surveillance results indicate continuing, often focal outbreaks of influenza virus types A(H3N2) and A(H1N1); influenza virus type B was isolated less frequently. Several examples follow.

Asia: In Hong Kong, influenza A(H3N2) activity peaked in March and was replaced in June by influenza A(H1N1) virus. In Singapore, where type A(H3N2) virus had been isolated earlier in the year, type A(H1N1) strains also began to be isolated in markedly increased numbers in late May and June. A few type B viruses also were isolated in both countries during the same period. Limited outbreaks of influenza in Guandong Province, Peoples Republic of China, were associated with isolates of a few A(H3N2) viruses and an A(H1N1) virus where type A(H3N2) virus had been isolated earlier in the year, type A(H1N1) strains also began to be isolated in markedly increased numbers in late May and June. A few type B viruses also were isolated in both countries during the same period. Limited outbreaks of influenza in Guandong Province, Peoples Republic of China, were associated with isolates of a few A(H3N2) viruses and an A(H1N1) virus in May and June. In Taiwan Province and in Bangkok, Thailand, A(H1N1) viruses were isolated from June to August.

Africa: Several type A(H3N2) viruses and a single type B virus were isolated from sporadic cases in Madagascar in March and April. In Johannesburg, South Africa, an outbreak of type A(H3N2) influenza occurred in July.

Oceania: An outbreak of type A(H1N1) virus was confirmed by virus isolation in New Caledonia during March. Starting in May, type A(H1N1) activity was also implicated in outbreaks in New Zealand, particularly in South Island. In contrast, type A(H3N2) viruses predominated in the central and northern parts of North Island. In Tasmania, Australia, an outbreak of type A(H1N1) occurred in July, but elsewhere in Australia, generally low levels of influenza A(H1N1) and A(H3N2) virus isolation were reported. Type B influenza viruses were also isolated occasionally in both countries.

Americas: Type A(H3N2) virus was isolated in French Guyana during March and in Uruguay during July. In Santiago, Chile, type A(H1N1) virus was isolated from young adults during July. In Belem, Brazil, A(H3N2) strains were most frequently isolated during a period of activity that peaked in May and June. Sporadic cases of A(H1N1) virus were reported in April in San Paulo, and type B virus was isolated in Rio de Janeiro. Type A(H3N2) virus caused an outbreak in Jamaica during July (see below), and in August, an A(H3N2) virus was isolated in the United States from a young adult who became ill in Colorado 2 days after returning from a 5-day visit to Mexico.

Antigenic analysis of A(H3N2) strains received at CDC indicates nearly all are very closely related to A/Philippines/2/82(H3N2), which replaced A/Bangkok/1/79 as the A(H3N2) component of the vaccine prepared for the 1983-1984 influenza season.

Jamaica: From July 12 through August 4, 1983, an outbreak of respiratory illness with 19 associated deaths was reported among the 591 residents of a facility housing chronically ill and indigent people in Kingston, Jamaica (Figure 1). Four of eight throat and nasopharyngeal cultures obtained from ill residents yielded influenza A(H3N2) virus similar to A/Phillippines/2/82.

Because body temperatures and other specific clinical manifestations of illness were not routinely documented during the outbreak, a case of respiratory illness was defined as a person with feverishness, cold symptoms, or acute cough from July 12 through August 4. Fever and cold symptoms were reported in 62 (91%) of 68 cases among residents, and cough was reported in 53 (78%). Three cases, but no deaths, were reported among the 149-member, predominantly female staff.

The outbreak was largely confined to the facility's male-resident wards. Thus, 66 (97%) of the 68 cases occurred among 328 adult male residents (attack rate 21%), probably because the women's and children's wards were geographically separate from the men's, and there was little interaction between residents and staff from the two areas. Men aged 70-89 had the highest attack rate (35%).

Preliminary analysis suggests that residents with diagnoses of cardiovascular disease, malnutrition, and senility were at higher risk of acquiring illness and subsequently dying. The case-fatality ratio for persons with these diagnoses was 53%, compared to an overall case-fatality ratio of 28%. There is no evidence of widespread influenza activity in Jamaica, and there have been no laboratory-documented cases in the community this summer. Reported by Diagnostic Virology Section, Epidemiology Div, US Air Force School of Aerospace Medicine, San Antonio, Texas; Virus Diseases Unit, World Health Organization, Geneva; A Dyer, MD, Dept of Microbiology, Univ of West Indies, Kingston, Ministry of Health, influenza activity in Jamaica, and there have been no laboratory-documented cases in the community this summer. Reported by Diagnostic Virology Section, Epidemiology Div, US Air Force School of Aerospace Medicine, San Antonio, Texas; Virus Diseases Unit, World Health Organization, Geneva; A Dyer, MD, Dept of Microbiology, Univ of West Indies, Kingston, Ministry of Health, Jamaica; Caribbean Epidemiology Centre, Port-of-Spain, Trinidad; Pan American Health Organization, Washington, DC; Div of Field Svcs, Epidemiology Program Office, International Health Program Office, WHO Collaborating Center for Influenza, Influenza Br, Div of Viral Diseases, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: The past several months' surveillance data are consistent with the previously detected trend toward displacement of A/Bangkok/1/79(H3N2)-like strains by A/Philippines/2/82(H3N2)-like strains (1), which have caused outbreaks in all continents where influenza has recently been active. These data also indicate that A(H1N1) virus is still cocirculating with A(H3N2) strains, and in certain times and places, have predominated. The generally low level of influenza B virus worldwide is typical of that observed in many recent years between periods of greater activity.

The public and health-care providers should be aware that, although influenza activity remains unpredictable for next winter, the potential for severe impact always exists, particularly in the elderly and other high-risk groups (2), as illustrated by the Jamaica outbreak. Influenza vaccine may reduce morbidity and mortality in such groups and has been strongly recommended by the Immunization Practices Advisory Committee (2). Since influenza activity usually peaks in the United States during January to March, with major activity rarely occurring before mid- to late-December, it is preferable to administer vaccine during mid to late fall to maximize chances that immunity will persist until spring.

References

1. CDC. Antigenic analysis of recent influenza virus isolates. MMWR 1983;32:195-6, 201.

2. CDC. Influenza vaccines, 1983-1984. MMWR 1983;32:333-7.

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