Flu Scan for Apr 01, 2015

News brief

Study: High-dose flu vaccine cut hospitalization risk only in very elderly

A study involving more than 160,000 elderly US military veterans suggests that the high-dose (HD) influenza vaccine didn't lower their risk of hospitalization for flu or pneumonia overall, compared with standard-dose (SD) vaccine, but it did reduce the risk for those 85 and older.

The HD vaccine, which contains four times as much antigen as SD vaccine, is intended to boost protection in elderly people, who have a weaker immune response to vaccines than younger people do.

Researchers in Philadelphia focused on patients who received primary care at Veterans Health Administration (VHA) hospitals and who received flu vaccine in the 2010-11 flu season, when the match between the flu vaccine and circulating flu strains was said to be excellent. Their report was published yesterday in Clinical Infectious Diseases.

The study included 25,714 HD vaccine recipients and 139,511 SD vaccinees at 23 VHA medical centers. The rate of hospitalization for flu or pneumonia during the flu season was 0.3% in both groups. The authors did not gather data on the number of lab-confirmed flu cases.

Most of the patients were men. Compared with SD recipients, the HD recipients were slightly older, more likely to be black, had more comorbidities, and were more likely to have HIV and exposure to immunosuppressive drugs.

After adjusting for the differences in patient characteristics, the authors found that the risk of hospitalization for flu or pneumonia was not significantly lower in the HD group overall than in the SD group (risk ratio, 0.98; 95% confidence interval [CI], 0.68-1.40).

But among patients who were 85 or older, the hospitalization rate for flu or pneumonia was significantly lower in the HD group: 0.30% versus 0.66% (risk ratio, 0.52; 95% CI, 0.29-0.92).

The authors conclude that more studies are needed to evaluate the benefits of the HD vaccine and to find other ways to increase the immunogenicity of flu vaccines in elderly people.
Mar 31 Clin Infect Dis abstract
Related Feb 9 CIDRAP News item

Study suggests human spread of H7N9 increased slightly in 2nd wave

An analysis of disease-onset data from China's H7N9 outbreaks in 2013 and early 2014 produced some evidence of increased human-to-human transmission in the second wave of cases, a team of British and US researchers reported today in Emerging Infectious Diseases.

The team focused on the provinces that had the six largest outbreaks: Shanghai, Zhejiang, and Jiangsu in the first wave, in the spring of 2013, and Guangdong, Zhejiang, and Jiangsu in the second wave, from November 2013 to May 2014. In addition to examining human transmission, the researchers assessed how much bird-market closures reduced animal-to-human transmission.

They said previous studies of H7N9 suggested that the basic reproduction number—R₀, the average number of secondary cases generated by a typical infected person in a fully susceptible population—was higher in some disease clusters than others, although there was no sustained transmission.

The researchers said they found evidence of "a small but significant amount of transmission between humans in the first and second waves" of cases. The estimated reproduction number for Jiangsu did not change significantly between the first and second waves, but for Zhejiang, R₀ increased significantly between the two waves, from 0.06 (95% credible interval [CrI], 0.00–0.25) to 0.35 (95% CrI, 0.15–0.65) (P = .045).

In addition, the team identified five case clusters involving human transmission during the first wave and eight such clusters in the second wave. In both waves the median size of the clusters was two cases.

The analysis also showed that market closures were very effective in reducing the risk of animal-to-human transmission, but the reduction was lower in Guangdong than in the other provinces.
Apr 1 Emerg Infect Dis report

News Scan for Apr 01, 2015

News brief

Study: C diff type 027 predicts severe outcome

Infection with Clostridium difficile ribotype 027 independently predicts severe disease and mortality, but demographic and clinical factors are stronger predictors of severe disease, according to a study yesterday in Clinical Infectious Diseases.

A US team analyzed data from 1,144 patients who had C difficile. They found that detection of stool toxin A or B by enzyme immunoassay did not predict severe disease or mortality, whereas infection with type 027 independently predicted both (adjusted odds ratio of 1.73 and 2.02, respectively).

However, concurrent antibiotic use, metastatic cancer, congestive heart failure, liver disease, and using a proton pump inhibitor were all stronger predictors of severe disease, 30-day mortality, or both. And being female was associated with a 2.48 adjusted odds ratio of severe disease.

In a related commentary, Abraham Goorhuis, MD, PhD, of the Center for Tropical and Travel Medicine at the University of Amsterdam, said, "This study adds to the body of evidence that the type 027 strain is intrinsically virulent. . . However, in the individual patient, demographic and clinical parameters seem to be stronger predictors."
Mar 31 Clin Infect Dis abstract
Mar 31 Clin Infect Dis commentary (subscription required)

CDC says it didn't pinpoint cukes as Salmonella cause till too late

An official with the Centers for Disease Control and Prevention (CDC) said the reason that the agency didn't report until this February on a cucumber-related Salmonella outbreak that occurred last summer was because the investigation did not determine the source until it was too late to help the public, Food Safety News reported today.

Matthew Wise, PhD, MPH, who led the outbreak response team, said the CDC first suspected tomatoes in part because the genetic fingerprint of the outbreak strain matched one associated with numerous outbreaks in recent years caused by tomatoes grown in the Delmarva growing region of Maryland. In mid to late August, officials noted that a large number of patients lived in or traveled to the Delmarva region.

In September, however, the investigation shifted to cucumbers, which are a much less common source of Salmonella infections. And it took till late September before scientists could trace the cucumbers back to a single farm. By then, Wise said, it didn't make much sense to send out an alert because cases had tapered off. The last illness appeared on Sep 30.

The short shelf life of cucumbers was also a factor, as customers weren't likely to still have them in their homes, the story said. The CDC first detailed the outbreak, which included at least 275 patients, in a Morbidity and Mortality Weekly Report (MMWR) update on Feb 20.
Apr 1 Food Safety News story
Feb 20 CIDRAP News scan on MMWR report

WHO details late 2014 Lassa fever outbreak in Benin

A Lassa fever outbreak in Benin in West Africa involving at least 16 cases and 9 deaths in November first caused concern about possible Ebola, the World Health Organization (WHO) said yesterday in an update.

Local and WHO officials were first alerted to the outbreak after four hospital workers in Tanguieta in the northwestern part of the country died over the course of 2 weeks from a severe febrile illness, some with signs of hemorrhagic fever.

After tests ruled out Ebola, Lassa fever was suspected, even though the nation had never had a confirmed case, because cases were reported last year in Nigeria, Benin's neighbor to the east. Lab tests confirmed the diagnosis.

A woman living in a village near Tanguieta had died from Lassa fever 2 days after giving birth to a girl. The baby fell sick at 2 weeks and was taken to the hospital, which led to the infection and death of a pediatrician, two other health professionals, a language interpreter, and other patients and contacts. An international team and national health officials initiated an Ebola-type response plan, and the outbreak was brought under control quickly, with no new cases since late November.

"The measures the team introduced brought the Lassa fever outbreak quickly under control, and they would have been just as effective for an Ebola outbreak," said Dr. Youssouf Gamatie, Benin's WHO representative.
Mar 31 WHO report