CDC: 9 more H3N2v cases reported in Maryland, Michigan
In its latest weekly FluView report today, the US Centers for Disease Control and Prevention (CDC) said it has received reports of nine more variant H3N2 (H3N2v) influenza cases, eight from Maryland and one from Michigan, its first of the year.
The CDC said all nine patients reported exposure to pigs at two fairs in the week before they became ill. Eight are children and one is an adult older than 50. One of the patients was hospitalized, but all are recovering or have recovered. Investigators have found no human-to-human transmission. Six of the eight cases have been confirmed as H3N2v and three are presumed positive based on testing at Maryland's public health lab.
Maryland has reported several human cases since the middle of September, and the CDC said the state's number of cases is declining. The CDC said the Michigan case isn't related to the ongoing investigation in Maryland. The Michigan patient is a child who had recently visited the Allegan County Fair, which took place Sep 8 through Sep 16, according to a statement from the Allegan County Health Department (ACHD). Allegan is in southwestern Michigan.
The Maryland Department of Health (MDH) in its latest update said 40 presumptive positive and confirmed cases have been detected as of Oct 4. The total reflects an increase of 3 cases since an update earlier this week. Two people were hospitalized.
So far this year, 61 variant flu cases have been reported to the CDC, 56 of them involving H3N2v, 3 due to H1N2v, and 3 presumed H3N2v positives from Maryland undergoing further CDC testing.
Oct 6 CDC FluView report
Oct 6 ACHD statement
Oct 6 MDH case count
H7N9 features keep CDC experts on high alert
In an update on H7N9 avian influenza in China at the ID Week meeting in San Diego this week, Tim Uyeki, MD, MPH, an expert with the CDC's influenza division, pointed out several features of the virus and the disease that have the CDC closely following the developments.
He said the CDC has identified three viruses as highest risk, and H7N9 raises the greatest concerns. The other two are H5N6 and H5N1, according to a report yesterday from Infectious Disease Special Edition. When H7N9 emerged in humans 2013, it was the first time a low-pathogenic virus caused fatal infections in humans, raising alarm at the CDC and elsewhere.
Uyeki said that, of 40 clusters reported so far, a little more than a third involved secondary infections with a close contact, usually in a household member without poultry exposure. No transmission beyond two generations have been reported, he said. H7N9's appearance in health settings in unrelated people, including patients and health workers, underscores the important of carefully following infection control protocols, he added.
Until the fifth wave, which wound down over the summer, experts had seen little antigenic drift, but the most recent surge of activity last winter was marked by the emergence of a highly pathogenic form, which has so far been confirmed in 28 patients in five of China's provinces.
"We really need to keep our eye on this," he said, adding that another concern is increased receptor binding. H7N9 is unusual, because it can infect both lower and upper respiratory tracts. "This is a significant pandemic advantage for the virus."
Other worries are that resistance to neuraminidase inhibitors isn't present in the poultry viruses, but it has evolved during patient treatment. Though resistance has increased from 4% to 10%, it is still uncommon, and clinicians recommend early treatment with neuraminidase inhibitors, he said.
Uyeki, however, said high-dose corticosteroids should be avoided, because they have been associated with prolonged viral shedding, nosocomial infection, ventilator-associated pneumonia, and increased mortality at 30 and 60 days.
Oct 5 Infectious Disease Special Edition story