Study finds new clues behind severe H7N9 infection
The severity of H7N9 influenza infection is linked to high cytokine levels, and some patients appear to have a genetic marker that correlates with more serious outcomes, according to a research team from China and Australia. The group reported their findings in the Dec 23 edition of Proceedings of the National Academy of Sciences (PNAS).
They examined cytokine and chemokine levels in plasma samples of 18 patients who were hospitalized in Shanghai with H7N9 infections. They also looked at bronchoalveolar lavage samples from three of the patients and conducted genetic sequencing tests on blood and lung samples.
When they compared the clinical courses with the test results, they found that H7N9 severity was associated with higher levels of cytokines and chemokines, a pattern seen with other types of influenza infections, such as H5N1. They showed that cytokine levels were 100- to 1,000-fold higher in plasma than in lungs, and the authors said hat plasma levels may provide a "window" for assessing cytokine damage in infected lungs. The researchers also identified a genotype that related to more severe clinical outcomes: IFN-induced transmembrane protein-3 (IFITM3).
Peter Doherty, PhD, laureate professor at the University of Melbourne and lead author of the study, said in a Dec 23 press release that predicting how flu affects individuals could provide keys to managing the disease and allocating health resources. "We are exploring how genetic sequencing and early identification can allow us to intervene in treating patients before they become too unwell. As new cases of influenza emerge in the Northern Hemisphere, we try to keep a season ahead and prepare to protect the most vulnerable in our community," he said.
In other developments, Hong Kong's government today said an 80-year-old man hospitalized in early December with an H7N9 infection has died, according to a Reuters report. His case is one of two H7N9 cases recently imported into Hong Kong from the mainland city of Shenzhen and is now Hong Kong's first fatal case. The man's death pushes the number of fatal H7N9 cases to 48. Overall, 146 cases have been reported, all with links to mainland China, where the disease is thought to be spreading to people from infected market poultry.
Dec 23 PNAS abstract
Dec 23 University of Melbourne press release
Dec 26 Reuters story
CDC alerts health providers about H1N1 patterns, treatment
The US Centers for Disease Control and Prevention (CDC) issued a Health Alert Network (HAN) advisory to healthcare providers on Dec 24 that said it has received a number of reports of severe respiratory infections in young and middle-aged adults, many of whom were infected with the 2009 H1N1 virus.
The CDC said multiple hospitalizations and some deaths have been reported and the virus seems to be following a pattern seen during the pandemic months when it caused more illness in children and young adults. It warned that if the 2009 H1N1 virus—now considered a seasonal strain and covered in all flu vaccine formulations—continues to circulate widely, children and middle-aged adults may shoulder much of the burden.
The agency reported that so far there is no sign of significantly increased virulence or transmissibility, but the CDC will continue to watch for changes in the virus' genetic sequences and in disease surveillance systems. Some people who have had severe H1N1 infections this year had underlying medical conditions such as pregnancy and obesity, but others did not.
The CDC urged health providers to recommend seasonal flu vaccination, and it encouraged them to consider antiviral treatment as early as possible for any patient with confirmed or suspected flu who has a severe, complicated, or progressive infection or is at higher risk for complications.
Texas and a handful of other south-central states are the nation's flu hot spots to date, according to the most recent surveillance report from the CDC. Clusters of severe respiratory illnesses have surfaced at some Texas hospitals. The 2009 H1N1 virus has been confirmed in some of the patients, and some deaths have been reported, especially in the area around Houston.
Dec 24 CDC HAN notice
Dec 20 CIDRAP News story "Texas cluster part of rising H1N1 activity in state, nation"
H5N2 on Chinese poultry farm leads to culling of 125,000
An outbreak of highly pathogenic H5N2 avian influenza on a poultry farm in northeastern China has resulted in the culling of 125,700 birds, according to a World Organization for Animal Health (OIE) notice posted Dec 21.
The farm is located in the city of Baoding in Hebei province, about 140 kilometers southwest of Beijing. Symptoms of the disease began showing up in the farm's chickens Dec 17, and about 4,000 chickens died.
Samples from the diseased birds were confirmed as H5N2 by the National Avian Influenza Reference Laboratory. The farm has been placed under quarantine and disinfected.
Dec 21 OIE report
Dec 23 NBC News item on the outbreak
H7N1, H7N7 avian flu strains strike South African ostrich farms
Three outbreaks of low-pathogenic H7N1 avian influenza have been reported on commercial ostrich farms in Australia, according to an OIE notice posted Dec 24. They represent the most recent events in an outbreak that began in October.
The farms are located in Eastern Cape province. Sixty-four cases of subclinical infection have been confirmed among the 2,906 susceptible ostriches on the farms, for a morbidity rate of 2.20%. No birds have died of the disease or been culled. The farms have been disinfected and put under quarantine.
In another development in South African avian flu, a case of H7N7 avian flu has been reported in an ostrich on a commercial farm in Western Cape province. The farm has 1,005 susceptible birds, for a morbidity rate of 0.10%, according to a Dec 23 OIE follow-up report on the outbreak, which was first reported in February.
Dec 24 OIE report on Eastern Cape farms
Dec 23 OIE report on Western Cape farm
A related OIE follow-up report, this one pertaining to an outbreak of low-pathogenic H7 avian flu in South Africa beginning at the end of July, reported no new cases. The outbreak involved indigenous wild birds and an exotic parrot kept in captivity. The previous report noted 4 cases among 2,000 susceptible birds, for a morbidity rate of 0.20%.
Dec 23 OIE report on South African birds
Testosterone-regulated genes may suppress flu-vaccine response in men
The body's response to influenza vaccine may be influenced by testosterone-regulated genes, helping to explain why men often show a less-robust response to vaccines, in particular influenza vaccines, than women, according to a study released Dec 23 in the Proceedings of the National Academy of Sciences (PNAS).
In the National Institutes of Allergy and Infectious Diseases (NIAID)–funded study, researchers from Stanford University used a systems analysis approach to study antibody responses to the 2008-09 trivalent seasonal flu vaccine (TIV) in 53 women and 34 men of different ages.
The authors found that the women, compared with the men, had elevated antibody responses to TIV and elevated expression of inflammatory cytokines. They traced the weaker responses in men to a tendency toward high expression levels of a cluster of genes that participate in lipid biosynthesis and that have been found previously to be up-regulated by testosterone.
The men with the highest levels of testosterone and most elevated expression of the gene cluster had the weakest antibody responses to the TIV. In their discussion, the authors note that from an evolutionary perspective, the immunosuppressive effects of testosterone may act as a homeostatic mechanism to, for example, protect against the potentially deadly cytokine storm that can occur in healthy males in the presence of pandemic influenza.
Dec 23 PNAS study
Dec 23 NIAID news release on the study