News Scan for May 05, 2016

Saudi MERS case
Single-dose cholera vaccine
Worrisome H5N6 evolution

Saudi Arabia reports asymptomatic MERS infection in Riyadh

Saudi Arabia's Ministry of Health (MOH) today reported an asymptomatic MERS-CoV infection in a man in Riyadh who is a household contact of a previous MERS patient.

The new MERS-CoV (Middle East respiratory syndrome coronavirus) case—just the country's fifth in 2 weeks after a surge of cases in March and early April—involves a 39-year-old foreign man who is not a healthcare worker. The MOH provided no further details about the man or his household contact, as is its wont.

The new case brings the country's MERS total since 2012 to 1,381, including 590 deaths. Seven MERS-CoV patients are still undergoing treatment.
May 5 Saudi MOH update


Study: Single dose of oral cholera vaccine protects older kids and adults

One dose of killed oral cholera vaccine reduced cases of the disease by 40% in a cholera-endemic area, according to a study today in the New England Journal of Medicine.

Researchers from Bangladesh, South Korea, and the United States evaluated the efficacy of a single dose of the killed oral cholera vaccine Shanchol in 102,552 people ages 1 year and older living in Dhaka, Bangladesh, compared with a group of 102,148 people who received a placebo. Shanchol is currently administered in a two-dose schedule, and in 2015 the regimen's efficacy was determined to be 53% over 2 years.

During 6 months of follow-up, 101 cases of cholera occurred in the study groups, 37 of which caused severe dehydration. The vaccinated group experienced a lower rate of cholera episodes (0.37 cases per 1,000 people) compared with the placebo group (0.62 per 1,000), and vaccine protective efficacy for all cholera cases was 40%. The protective effect for a single dose was higher for severely dehydrating cholera cases, which were reduced by 63% in vaccinated people.

A single dose appeared to convey little protection for children under the age of 5, however. Vaccine efficacy for children ages 1 to 4 years was 16% (95% confidence interval [CI], -49%-53%) for all cholera cases and 28% (95% CI, -221%-84%) for severely dehydrating disease. Protective efficacy against all cholera episodes in children ages 5 to 14, in contrast, was 63% (95% CI, -39%-90%), and in people 15 years and older it was 56% (95% CI, 16%-77%).

While a two-dose regimen of killed cholera vaccine remains ideal, a single dose appears sufficient for older children and adults when the recommended schedule proves difficult or impractical, the authors said. They added that children under the age of 5 should receive two doses whenever possible.
May 5 N Engl J Med study


Report notes H5N6 mutations in humans, some worrisome

The genetic makeup of H5N6 avian flu isolates from two people infected in Guangdong province, China, in December 2015 differs fairly substantially from human isolates from the same province in 2014 and shows evidence of increased resistance, a worrisome sign, according to a letter yesterday in Emerging Infectious Diseases.

Chinese researchers said that although the hemagglutinin and neuraminidase genes were similar in the 2015 and 2014 viruses, all six internal genes differed.

The PB-2 gene from one of the 2015 isolates appears to have been derived from an H6N6 virus isolated from a duck, while all its other genes were derived from H5N6 viruses that have been circulating in poultry since 2013. The other 2015 isolate showed high nucleotide identity with an H5N6 human virus collected in 2015 in Yunnan province. Its six internal genes appear to have come from H9N2 viruses in animals.

"These findings show that the circulating H5N6 virus in southern China has reassorted with enzootic H6N6 and H9N2 viruses, resulting in new H5N6 viruses that are capable of infecting humans," the authors wrote.

In addition, the 2014 human H5N6 isolates had no mutations associated with reduced sensitivity to adamantane antiviral drugs, but two of the three isolates from 2015 (the two from Guangdong and one from Yunnan) have the 31N amino acid in their M2 gene, suggesting that they have acquired resistance.

"Thus, this virus lineage could be a great threat to public health," the authors conclude.
May 4 Emerg Infect Dis letter

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