Bird Flu Transmitted Human to Human

September 5, 2007

Rooster Near Hanoi, VietnamIn a disturbing development, the Sydney, Australia Morning Herald newspaper reports that the first documented instance of bird flu being transmitted from person to person has been confirmed in Sumatra, Indonesia. Previous cases were thought to have only spread from animals to humans. Human-to-human transmission greatly increases the chances of a bird flu pandemic. The World Health Organization (WHO) has warned in the past that if the H5N1 avian influenza virus, which causes bird flu, mutated and could be transmitted from person to person, an ensuing global influenza pandemic would kill millions of people.

Dr. Ira Longini, Jr.Using computer analysis, the Fred Hutchinson Cancer Research Center in Seattle, Washington studied the deaths of seven Sumatran family members who died in April and May 2006; human-to-human transmission was suspected at the time but wasn’t confirmed until recently. Fortunately, the viral transmission didn’t spread beyond the infected family. The study’s senior author, Dr. Ira Longini, Jr., said: “The world really may have dodged a bullet with that one, and the next time we might not be so lucky.”

Altogether, bird flu has infected 322 people and killed 195 of them. It’s now estimated that the secondary-attack rate — the risk that one person will infect another — is about 29 percent, similar to the transmission rate of seasonal influenza in the United States.

Dr. Longini, a biostatistician, and his colleagues reported their findings in the Emerging Infectious Diseases journal, which is a publication of the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia. The research was performed with a computerized disease-transmission model which factored in the number of patients, the number of people potentially exposed to the virus, the incubation period of the virus and other variables, producing the first statistical confirmation of bird flu being transmitted from person to person.

Dr. David Heymann, WHO Director for Communicable DiseasesWhile Triono Soendono, head of research for the Indonesian Health Ministry, claimed that other experts had concluded that this wasn’t an instance of person-to-person transmission and refused to discuss the present findings, the WHO’s director for communicable diseases, Dr. David Heymann, said there had “likely been transmission through intimate or close contact.” Heymann also said that the WHO suspects person-to-person transmission of H5N1 in at least two other instances, including a case in which a Thai mother and daughter, who lived apart, both died of bird flu. It’s believed that the daughter contracted the virus while visiting her mother, who was hospitalized with bird flu. Dr. Margaret Chan, new chief of the WHO and a bird flu expert from Hong Kong, warned in January that “The next pandemic, if it occurs, will be very devastating. . .we are very concerned of the likelihood of a pandemic.”

The Longini team has developed a software tool, TranStat, to quickly test disease outbreaks to see whether epidemics or pandemics may be developing. It’s anticipated that the software will be available free of charge at the National Institutes of Health’s MIDAS (Models of Infectious Disease Agent Study) website.

Read more about bird flu.

Photo credit: Reuters/Kham

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