With more surveillance, flu patterns in Africa begin to emerge

Dec 17, 2012 (CIDRAP News) – Increased surveillance in recent years has begun to fill in some of the huge information gaps regarding influenza in Africa, which should eventually make it possible to develop or improve public health interventions, according to a big collection of articles published recently in the Journal of Infectious Diseases (JID).

One of the many reported findings is that several countries in West Africa didn't see their first case of pandemic 2009 H1N1 (pH1N1) flu until 6 months after the virus emerged in North America. Another article discusses the belated distribution and administration of the pH1N1 vaccine in Africa.

The collection consists of 27 reports involving close to 300 authors from more than 50 institutions, most of them based in 16 African countries, the US Centers for Disease Control and Prevention (CDC) said in a press release. The CDC's Influenza Division sponsored the special issue.

Until about 6 years ago, little effort had been made to understand the epidemiology, burden, and seasonality of flu in Africa, according to an editorial included in the collection. On a continent battling AIDS, tuberculosis, and malaria, the impact of flu has been considered "negligible," say the editorial writers, from the CDC, South Africa, and Madagascar.

But in 2006, after the spread of H5N1 avian flu to dozens of countries, a large number of groups joined to support pandemic flu preparedness in Africa. Participants included the CDC, the World Health Organization (WHO), the International Network of the Institut Pasteur, South Africa's National Institute for Communicable Diseases, and various others.

The resources provided by these partners have "led to heightened efforts to build influenza diagnostic and response capacity and to conduct influenza studies to develop a solid evidence base for influenza policies in Africa," the editorial says.

A prime example of the increased surveillance efforts is the African Network of Influenza Surveillance and Epidemiology (ANISE), which offers a report on 5 years of surveillance in 15 countries across Africa. From 2006 to 2010, the number of ANISE sites collecting data on patients with influenza-like illness (ILI) increased from 21 to 127.

Children 0 to 4 years old accounted for 48% of patients with ILI or severe acute respiratory infection (SARI) who were seen at ANISE sites over the 5 years, according to the report. Twenty-two percent of ILI cases and 10% of SARI cases were positive for flu.

The ANISE researchers found that the flu had winter peaks in the North African countries in the network—Egypt and Morocco, which are temperate—and in South Africa. Seasonality was less clear in countries elsewhere, but East African nations had higher prevalence from July through October.

Another research team examined the circulation of flu in five countries—Cameroon, Cote d'Ivoire, Madagascar, Niger, and Senegal—in 2008 and 2009. Of 8,312 specimens tested, H1N1 was found in 329, H3N2 in 689, and type B in 148. Flu circulated year-round in some countries but was limited to part of the year in others.

To examine pH1N1 circulation in West Africa, another group collected surveillance data from 10 countries in the region from May 4, 2009, to Apr 3, 2010. More than 10,000 specimens were tested during that time, of which 25% were positive for flu.

Through the end of 2009, the authors found, only 14% of the flu cases were pH1N1. The proportion then jumped to 89% for January through Apr 3 of 2010. Further, five countries didn't record a single pH1N1 case until 6 months after the pandemic virus's North American emergence in April 2009. In seven countries, the virus didn't achieve predominance until 2010.

The authors say pandemic activity began in June or July of 2009 in most other parts of Africa, and it is unclear why circulation was delayed in West Africa. They write that sentinel surveillance systems with the ability to detect and subtype flu viruses were functioning in most of the countries in the study, so the delay was probably not an artifact of poor surveillance.

Distribution of pH1N1 vaccine in Africa didn't begin until February 2010, according to another JID report. Authors from the CDC and WHO wrote that 32.2 million doses were distributed to 34 African countries between February and November 2010.

Countries that reported their vaccination efforts to the WHO received 19.2 million doses, of which 12.2 million were administered, the article says. Population coverage varied from 0.4% to 11% in these countries, with a median of 4%.

All the countries targeted pregnant women and healthcare workers for vaccination, the team found. Fourteen of 19 countries vaccinated people with chronic health conditions, and 10 of 19 vaccinated children. But most of the doses were distributed after the peak of pH1N1 circulation in the region.

The CDC in its press release said the collection also offers "groundbreaking evidence on the epidemiology of influenza disease in Ethiopia, Tanzania, Rwanda, the Democratic Republic of Congo, and Angola," along with data on the flu contribution to respiratory illness from population-based studies.

"As more data are collected, ministries of health will see with increasing clarity who is most impacted by flu, if a vaccine policy would be beneficial, and when during a calendar year flu vaccine should be administered to prevent as much flu-related illness and death as possible," the CDC said. The agency added that such data are important for attracting flu vaccine donations.

See also:

Table of contents for Dec 15 JID supplement

Dec 15 JID editorial

Dec 14 CDC press release

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