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Update: influenza activity--worldwide, April-September 1998
Abstract:
In collaboration with the World Health Organization (WHO), the WHO international network of approximately 110 collaborating laboratories in 83 countries, and U.S. state and local health departments, CDC conducts surveillance to monitor influenza activity and to detect antigenic changes in the circulating strains of influenza viruses. During October 1997-April 1998. influenza activity was moderate to severe in the Northern Hemisphere. Influenza A(H3N2) viruses were predominant, but influenza A(H1N1) viruses were associated with outbreaks, and influenza B viruses were identified sporadically in all regions. Since April 1998, increased influenza outbreak and epidemic level activity, primarily associated with influenza A(H3N2), has been reported in the Southern Hemisphere. This report summarizes worldwide influenza activity during April-September 1998 and the antigenic characteristics of influenza isolates collected during April-September.
Insights
Global influenza surveillance detected moderate to severe activity in the Northern Hemisphere and increased outbreaks in the Southern Hemisphere. Influenza A(H3N2) viruses predominated, with other strains also circulating.
Area of Science:
- Virology
- Epidemiology
- Public Health
Background:
- The World Health Organization (WHO) collaborates with global laboratories and U.S. health departments for influenza surveillance.
- Monitoring influenza activity and detecting antigenic changes in circulating viruses are crucial for public health.
- Previous surveillance covered the Northern Hemisphere from October 1997 to April 1998.
Purpose of the Study:
- To summarize global influenza activity from April to September 1998.
- To analyze the antigenic characteristics of influenza virus isolates during this period.
- To inform public health strategies for influenza prevention and control.
Main Methods:
- Global surveillance data collection through the WHO international network of collaborating laboratories.
- Analysis of influenza virus isolates from approximately 110 laboratories in 83 countries.
- Monitoring of U.S. state and local health department reports.
Main Results:
- Influenza activity was moderate to severe in the Northern Hemisphere (October 1997-April 1998).
- Influenza A(H3N2) viruses were predominant, with co-circulation of A(H1N1) and influenza B viruses.
- Increased influenza outbreak activity, mainly A(H3N2), was reported in the Southern Hemisphere (April-September 1998).
Conclusions:
- Influenza A(H3N2) viruses were the primary cause of widespread influenza activity globally.
- Continued surveillance is essential for tracking viral evolution and informing vaccine composition.
- Public health efforts must adapt to regional and seasonal influenza patterns.