Virus World

The Centers for Disease Control and Prevention and National Center for Immunization and Respiratory Diseases have provided updated results of a preliminary assessment of the H5N1 viruses identified in two human infections detected in Cambodia in 2023 based on their genetic sequences and gives an update on the epidemiological investigation. On February 26, 2023, the Institut Pasteur du Cambodge, in collaboration with the Cambodian Ministry of Health, shared the full genetic sequence of the H5N1 virus recovered from the patient who died in that country on February 22, 2023 The genetic sequence of the second case was later also shared by the Institut Pasteur du Cambodge. CDC has conducted a preliminary analysis of the genetic sequences of these H5N1 bird flu viruses. They are H5N1 viruses from clade 2.3.2.1c, which are different from the H5N1 viruses now spreading in U.S. wild birds and poultry, which are from clade 2.3.4.4b. These viruses are similar to past 2.3.2.1c viruses detected in that geographic area over recent years. The genetic sequences suggest that an existing clade 2.3.2.1c candidate vaccine virus (CVV), called NIBRG-301 (A/duck/Vietnam/NCVD-1584/2012-like) would offer protection against the viruses identified in Cambodia.

Additionally, there were no genetic changes identified that are known to be associated with increased ability to spread to people or reduce susceptibility to influenza antiviral drugs. CDC had requested virus samples from both cases in Cambodia in order to conduct additional laboratory testing/analysis to confirm these and other characteristics of the viruses and to provide a more detailed risk assessment. CDC continues to support the Ministry of Health, Ministry of Agriculture, Animal, Forestry and Fisheries, and Ministry of Environment, in its ongoing One Health investigation. Evidence to date continues to support the conclusion that these two human infections are the result of two instances of bird-to-human spread. There is still no indication of person-to-person spread associated with these two cases. The investigation has revealed that both patients became sick at about the same time and were likely exposed to sick or dead poultry prior to becoming ill, including being near sick/dead poultry kept in a coop under the house or through butchering, cleaning, and cooking chicken that died. Investigation and containment efforts continue, including monitoring and/or testing of contacts of the two cases for 10 days after their last exposure, along with active surveillance for influenza-like-illness in the village. CDC will provide additional updates as needed.

Two family members were infected with H5N1; the daughter died. Eleven contacts, some with symptoms, have tested negative, according to the W.H.O. After a father and daughter were diagnosed with bird flu, officials in Cambodia scrambled to test nearly a dozen of their contacts for infection the H5N1 virus, which has been causing mass die-offs of birds worldwide. The daughter, an 11-year-old, has died, but the World Health Organization said on Friday that 11 contacts have so far tested negative for the infection. Why the concern? While hundreds of human cases have occurred over the years, scientists have become increasingly concerned that the virus one day may become adapted to people. Any evidence of human-to-human transmission would accelerate worries that a new pandemic could be on the way. Most experts believe that the cases in Cambodia were likely caused by direct exposure to infected birds. At the moment, the risk to most people remains low, they say.

Cambodia has reported two cases of bird flu infection in people, a father and daughter in a village in Prey Veng Province. The 11-year-old girl died earlier this week. The cases, the first reported in Cambodia since 2014, raised fears that the virus had acquired the ability to spread among people and may trigger another pandemic. But the World Health Organization said on Friday that 11 contacts of the girl, four of whom have flulike symptoms, had tested negative for infection with the H5N1 flu virus. Cambodian authorities said on Saturday that the father was infected with a strain that is endemic in the country, and was unrelated to the outbreaks in birds in the United States and Europe. The 49-year-old was not showing any symptoms, according to the Health Ministry. The W.H.O. is working closely with the Cambodian government to determine whether the father and daughter both caught the virus from direct contact with infected birds — the most likely possibility — or whether they infected each other. Experts noted that there had been hundreds of sporadic cases of H5N1 infection in people since the virus was first identified and that there was no evidence that it had become adapted to humans.

An 11-year-old girl in Cambodia has died of H5N1, the strain of avian influenza which has spread around the world and raised concern about a possible threat to human health, officials say. A girl in Ecuador tested positive last month. The Infectious Diseases Department at Cambodia’s Ministry of Health said the young girl, who lived in Roleang village in Prey Veng province, fell ill last Thursday when she developed a cough and a fever of 39°C (102°F). “After receiving treatment at the local level, the girl started to get tired and was sent to the National Children’s Hospital in Phnom Penh for treatment,” the department said in a statement. The girl died on Wednesday and she was buried in her village. A few hours later, a sample which was sent to the National Institute of Public Health tested positive for H5N1 bird flu. There was no immediate word on how or when the girl was infected but villagers told investigators that an unusual number of wild animals had recently died. An emergency response team has been sent to the area. The current variant of H5N1 has caused outbreaks around the world since late 2021, even in countries where bird flu had never been found. Since then, more than 50 million birds have been culled in Europe and nearly 58 million in the U.S.

The global spread of bird flu has raised concern about the possibility of a future variant which could lead to human-to-human transmission. Recent cases in mammals – including in mink, foxes and sea lions – have added to those concerns. “H5N1 has spread widely in wild birds and poultry for 25 years but the recent spillover to mammals needs to be monitored closely,” WHO Director-General Tedros Adhanom Ghebreyesus said earlier this month. Tedros added: “For the moment, WHO assesses the risk to humans as low. … But we cannot assume that will remain the case and we must prepare for any change in the status quo.” The World Organization for Animal Health (WOAH) echoed those concerns. “The current situation highlights the risk that H5N1 avian influenza may become better adapted to mammals and spill over to humans and other animals,” the agency said on February 13. “Some animals, such as mink, may act as mixing vessels for different influenza viruses, leading to the emergence of new strains and subtypes that could be more harmful to animals and/or humans.” A 9-year-old girl in Ecuador tested positive for H5N1 bird flu in January, making it the first such case in South America. She was hospitalized in critical condition but has since recovered. Another person died of H5N1 in China. Earlier this month, Peru reported that nearly 600 sea lions and 55,000 birds, including pelicans and penguins, are believed to have died of H5N1 bird flu. A dolphin and a lion also died of bird flu.

Ms. Youk Sambath, Secretary of State of the Ministry of Health, has confirmed that the Ministry of Health's emergency response team has found 12 more people possibly infected with Highly Pathogenic Avian Influenza A(H5N1) in Prey Veng province.  This marked the first case of death from bird flu since 2014 and the 57th case in the Kingdom. Between 2005 and 2014, the government reported 37 H5N1-related deaths. The Secretary of State stated that four of the affected people have begun to show symptoms. She added that the emergency response team took their samples for analysis at a laboratory in Phnom Penh and the results will be released today. The Health Ministry said its emergency response teams are investigating the area where the case happened. The statement said “an irregular number of dead wild animals” were found near the place where the infected girl lived. Samples from the dead animals were taken for lab testing and the ministry is awaiting the results.

Ms. Youk Sambath also said that the Ministry of Health’s emergency response team will continue to search for those affected by bird flu in schools tomorrow. With the discovery of the infected people , Ms. Youk Sambath called on the villagers to increase vigilance, health care and follow the instructions of professional officials. Public health expert Dr Quach Mengly said the disease has symptoms similar to a cold, cough, and fever and is highly life-threatening without treatment. “To prevent the infection, please avoid touching and eating sick and dead animals,” he said. “Bury the dead animals properly, and wash your hands properly after that.” Influenza A virus subtype H5N1 (A/H5N1) is a subtype of the influenza A virus which can cause illness in humans and many other animal species. A bird-adapted strain of H5N1, called HPAI A(H5N1) for highly pathogenic avian influenza virus of type A of subtype H5N1, is the highly pathogenic causative agent of H5N1 flu, commonly known as avian influenza (“bird flu”). It is enzootic (maintained in the population) in many bird populations, especially in Southeast Asia