Research: Flu on the brain

A study in Vietnam suggests that the H5N1 strain of avian influenza virus can affect the brain and central nervous system before respiratory problems appear. As antiviral agents are likely to work only early in disease, this could have important implications for avian flu treatment.

In February 2004, in Dong Thap Province in southern Vietnam, a sister and brother aged nine and four died within two weeks of each other.

Both children arrived in hospital having had fever, diarrhoea and increasing drowsiness for several days. In hospital, they went into coma and died. Respiratory symptoms appeared only during the last day of their lives. In both cases, acute encephalitis (brain inflammation) was reported as the cause of death.

However, because the boy was included in an ongoing research study, tissue specimens were taken. In November 2004, Menno de Jong and colleagues, at the Paediatric Hospital Number One, the Hospital for Tropical Disease and the Oxford University Clinical Research Unit in Ho Chi Minh City, isolated avian influenza virus strain H5N1 from all of these specimens. Given the similarity of symptoms, it is likely that his sister was also infected.

In humans, nervous system infection is an extremely rare complication of flu, but it is common in birds. Worryingly, H5N1 virus may be progressively adapting to mammals – and becoming more neurologically virulent. In addition, the presence of virus in faeces highlights a potential route of humanto-human transmission.

If the symptoms of H5N1 are more diverse than previously thought, clinical surveillance might need to focus not only on respiratory illnesses, but also on clusters of unexplained deaths or severe illnesses.

External links

• de Jong MD et al. Fatal avian influenza A (H5N1) in a child presenting with diarrhea followed by coma. N Engl J Med 2005;352(7):686–91.