May 18, 2006 (CIDRAP News) – An international team of scientists from the World Health Organization (WHO) and the US Centers for Disease Control and Prevention (CDC) arrived today on Indonesia's Sumatra island to investigate the largest cluster to date of confirmed human cases of H5N1 avian influenza, according to news services.
In addition, the WHO reported today that a 75-year-old Egyptian woman died of H5N1 infection, becoming the sixth fatality in Egypt.
In a news release about the Indonesian cluster today, the WHO said the source of infection was not yet known for any of the cases. "The possibility of limited human-to-human transmission cannot be ruled out," the agency said.
"A cluster is always serious," the WHO's Thomas Grein told Bloomberg news today after visiting North Sumatra. "This one by its sheer size and that it has occurred in an area where there have been no confirmed outbreaks is of course of interest."
In its statement today, the WHO gave some details on the cases in six extended family members from Kubu Sembelang village in the Karo district of North Sumatra—five of whom died—as well as on another Indonesian woman who died of avian flu in Surabaya in East Java. Her death was reported by news media yesterday.
In North Sumatra, the outbreak may have begun Apr 27 when a 37-year-old woman contracted a respiratory disease, which took her life May 4. However, no specimens were obtained from her body for confirmatory testing, but the WHO said she is considered the initial case in the cluster.
Her relatives, according to the WHO, constitute the six who tested positive for H5N1. The woman's 15-year-old son died of avian flu May 9, her 17-year-old son died May 12, her 10-year-old nephew died May 13, and her 28-year-old sister died May 10. The sister's 18-month-old daughter died May 14. In addition, her 25-year-old brother tested positive for H5N1 but is still alive.
These latest WHO confirmations raise Indonesia's case total to 40 (23 in 2006), with 31 deaths (20 in 2006), according to WHO data. Indonesia has reported by far the most cases and fatalities this year. Egypt has the second-most cases with 14 (6 deaths), and China has the second-highest death rate, with 7 deaths in 10 cases.
Although the WHO release about the cluster states that "If human-to-human transmission has occurred, it has not been either efficient or sustained," officials are concerned about the lack of an identified source for the virus.
"The source of exposure for the initial case is still under investigation, with exposure to infected poultry or an environment contaminated by their faeces considered the most plausible source," the agency said.
"The likely source of infection for the additional cases has not yet been determined," the statement continued. "Multiple hypotheses are being investigated. Apart from living in close proximity to each other, the cases in this cluster are known to have participated in a family gathering around 29 April. The cases may have acquired their infection from a shared environmental exposure yet to be identified."
"We have not yet found any evidence of the ongoing transmission among chickens in that area," said Shigeru Omi, WHO director for the Western Pacific region, as quoted in the Bloomberg story today. However, the story quoted Indonesia's agriculture minister as saying that 10 of 11 pigs tested in the district had antibodies to avian flu in their bloodstream, and about half of the 400 households in Kubu Sembelang raise pigs, chickens, and ducks.
Although the presence of antibodies in the pigs could signal a previous infection, "If the virus is in pigs, that would be a major concern," said Ton Schat, professor of virology and immunology at Cornell University, according to Bloomberg. Pigs are susceptible to both human and avian strains of influenza, and simultaneous infection with both types could allow viruses to trade genetic material, potentially giving rise to a hybrid that could spread among humans.
According to the WHO, instances of human-to-human H5N1 transmission have occurred, but in no case has the virus spread beyond people who have had close contact with an infected person, like family members.
In a Washington Post story today, Sari Setiogi, spokesperson for WHO's Indonesia office, said, "We are taking this very seriously. The good news is that, from our investigation to date, there's no evidence of further spread of the virus beyond the family."
In Egypt, WHO officials confirmed that a 75-year-old woman became Egypt's sixth death among 14 human cases of avian influenza, an AFP article said today.
The woman, from Al-Minya in southern Egypt, contracted the disease from infected birds, according to WHO regional health regulation officer John Jabbour. "She was admitted into the hospital yesterday, and she died today," Jabbour said in the AFP story.
WHO Indonesia report
WHO Egypt report
May 17 CIDRAP News story "WHO confirms avian flu case cluster in Indonesia"