A year after the World Health Organization announced it was on "high alert" over outbreaks of bird flu, China has confirmed the first human case of strain H7N4. Health officials say a 68-year-old woman who fell ill in Jiangsu province on Dec. 25 was infected with the strain, though she recovered after being admitted to the hospital on Jan. 1 and was released Jan. 22, per the Guardian. Officials haven't said whether there's an outbreak of H7N4 affecting poultry, but they note the woman was in contact with live poultry before developing symptoms, reports the South China Morning Post. H7N4 is one of nine known subtypes of H7 viruses, but unlike H7N2, H7N3, H7N7, and H7N9, it has never before been seen in humans.
Though still rare, H7N9 is among the most deadly strains for humans, having killed at least 600—about 40% of those hospitalized—since 2013, reports Reuters. Viruses H5 (with a mortality rate higher than 50%) and H9 (only one recorded death) have also been reported in humans, per the CDC. Alerted to the H7N4 case on Wednesday, Hong Kong's Center for Health Protection issued a travel alert ahead of a weeklong holiday for the Chinese Lunar Year, which begins Friday. Visitors to mainland China "must avoid visiting wet markets, live poultry markets, or farms," a rep says. "They should also avoid purchasing live or freshly slaughtered poultry, and avoid touching poultry/birds or their droppings." (Read more bird flu stories.)