CDC adds two novel H7N9 viruses to risk assessment list
In an update to its Influenza Risk Assessment Tool (IRAT), the US Centers for Disease Control and Prevention (CDC) yesterday added 2 more viruses, raising the total on the list to 15.
The two additions are both North American lineage H7N9 viruses detected in US poultry over the past two seasons, a highly pathogenic form found at a commercial farm in Tennessee and a low-pathogenic form found in commercial and backyard poultry in Tennessee and three other states. No human cases were detected in any of the outbreaks involving the North American H7N9 viruses, which are not related to the H7N9 influenza that has sickened hundreds of people in China in recent years.
The CDC uses two sets of criteria to assess novel viruses, one that looks at the potential for human-to-human spread and the other geared toward overall impact on public health. It said both viruses are in the low-risk category.
May 31 CDC summary of IRAT results
Nicaragua household study reveals Zika longevity in body fluids
A household study of people infected in Nicaragua's Zika virus outbreak in 2016 yielded new information on illness levels in contacts and symptom patterns. The study, conducted by a Nicaragua-based research team in 17 neighborhoods of Managua, appeared yesterday in PLoS Neglected Tropical Diseases.
Nicaragua experienced an explosive epidemic from June to September of 2016, and the study focused on cases reported in part of the capital city between Aug 31 and Oct 21 of that year. The researchers identified 33 lab-confirmed cases during the study period, along with 109 contacts, and followed them for 3 weeks, collecting clinical and demographic information, as well as lab samples that included blood, saliva, and urine.
They found that 62% of the people they followed had asymptomatic infections, consistent with earlier studies that put the percentage between 27% and 82%. They found that viral load in serum was relatively high before symptom onset, suggesting that asymptomatic infection may play an important role in virus transmission. Of the index patient households, 61% had contacts with Zika infection, with 1.9 positive contacts (range 1 to 6) per household. In 60% of households, more than 50% of members were positive for Zika infection, hinting that transmission was widespread among the affected families in Managua.
Analysis of viral load in different body fluids showed similar viral load levels, with serum showing the highest peak. Viral RNA was detectable in blood and saliva up to 7 days after symptom onset and was found in urine up to 22 days after symptom onset. The team noted that Zika RNA detection in saliva over a similar period hints that saliva tests might be useful as a more accessible diagnostic sample.
During their household visits, the researchers observed that 21% of the households had water containers that contained Aedes aegypti larvae or pupae.
The authors said their findings shed useful light on Zika in body fluids and help provide a snapshot of spread in an urban setting, especially regarding asymptomatic infections.
May 31 PLOS Negl Trop Dis abstract
New polio case recorded in Afghanistan, 8th this year
Afghanistan reported one new case of wild poliovirus type 1 in Kandahar, bringing the total number of cases recorded in 2018 to eight. Details of the latest case were published in the Global Polio Eradication Initiative's (GPEI's) latest weekly update.
The patient's symptoms began on Apr 27. In response to ongoing wild poliovirus transmission, health workers in the country vaccinated more than 9.6 million children with the bivalent oral polio vaccine during the month of May.
The GPEI also mentioned the recent World Health Assembly endorsement of a 5-year plan on transitioning to a polio-free world. If successful, poliovirus will join smallpox as the only diseases eradicated in history.
"Delegates noted that wild poliovirus transmission is now at the lowest ever levels in history," the GPEI said. So far only eight wild poliovirus cases have been reported this year, all from Afghanistan. Two African countries—the Democratic Republic of Congo and Nigeria—have reported a few circulating vaccine-derived poliovirus cases.
May 31 GPEI report
H7N9 avian flu outbreak strikes Chinese layer farm
China's agriculture ministry has reported an H7N9 avian flu outbreak at a layer farm in Liaoning province in the northeast, according to a government statement translated and posted today by Avian Flu Diary (AFD), an infectious disease news blog.
The farmer noticed symptoms in the flock on May 22, with the outbreak resulting in about 9,000 deaths. Provincial animal health officials confirmed the H7N9 findings—likely related to a highly pathogenic strain because of the symptoms and high numbers of deaths—on May 31. As part of the outbreak response, 8,000 surviving birds were culled.
Last summer China deployed a new vaccine against both H5 and H7 avian flu viruses in poultry across all of its provinces. Since then, few poultry outbreaks and human cases have been reported. China reported its last H7N9 outbreak in poultry in early May, a highly pathogenic event that struck a layer farm in Ningxia province in the country's northwest.
Jun 1 AFD post