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H5N1: Has there been human-to-human transmission, and do we have a vaccine?

BMJ 2023; 380 doi: (Published 02 March 2023) Cite this as: BMJ 2023;380:p510
  1. Elisabeth Mahase
  1. The BMJ

With H5N1 still a worldwide concern, Elisabeth Mahase looks at the latest developments, including preparations for a vaccine

What’s happening in Cambodia?

Much of the spotlight has been on Cambodia in the past week, where an 11 year old girl died after being infected with an H5N1 virus. The girl, from Prey Veng province in the south of the country, was admitted to the National Paediatric Hospital on 21 February with severe pneumonia and died a day later. The authorities notified the World Health Organization of the situation and shared the genetic sequencing data, which showed that the virus belonged to the influenza A virus subtype H5N1 but was the clade, different from the clade causing concern in other parts of the world.1

Of the girl’s 12 close contacts who were identified (four with symptoms, eight without), only one, the girl’s father, tested positive for H5N1. The others tested negative for H5N1 and for SARS-CoV-2.

Does this mean the virus has started to spread between people?

Not necessarily. Although the investigation into what happened in Cambodia is ongoing, WHO has said there was currently no evidence of human-to-human transmission. In an update it said, “While further characterisation of the virus from these human cases is pending, available epidemiological and virological evidence suggest that current A(H5) viruses have not acquired the ability of sustained transmission among humans, thus the likelihood of sustained human-to-human spread is low.”

Health officials in Cambodia have also said that the cases show no sign of human-to-human transmission.2

Why are scientists concerned about this H5N1 outbreak?

Although …

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