News Scan for Aug 09, 2016

Aerosol stability in Ebola
;
HIV and drug-resistant TB
;
Global flu status
;
Campylobacter infection in children
;
Chikungunya update

2014 Ebola strain no more viable than 1976 strain

A study yesterday in the Journal of Infectious Diseases suggests that although the Ebola outbreak originating in West Africa in 2013 was the deadliest to date, that strain of Ebola virus (EBOV) did not possess more aerosol stability than a strain of 1976 EBOV.

Previously, some scientists wondered if EBOV Makona, the strain behind the 2013-2015 outbreak, spread widely and quickly because the virus evolved and was more easily transmitted from person-to-person through aerosols. To test this hypothesis, researchers compared aerosols from EBOV Makona 2014 and EBOV Mayinga 1976.

"The rate at which the virus lost viability in an aerosol remained the same between the 2 viruses, indicating that the scope of the West African outbreak was not due to an increased stability of aerosolized virus," the authors wrote.

Study authors showed that both the 1976 and 2014 strains could survive for 3 hours as an aerosol at 22°C and 80% relative humidity.
Aug 8 J Infect Dis study

 

Study finds HIV does not promote spread of drug-resistant TB

Contrary to previous suspicions, HIV infection does not encourage the emergence and spread of multidrug-resistant tuberculosis (MDR-TB), according to a study based on an analysis of Mycobacterium tuberculosis isolates from patients in South America.

The report, written by a team of Norwegian, British, and Argentinian scientists and published today in eLife, says that MDR-TB is particularly common in areas where HIV infections are also common, but it was not known whether HIV directly promotes drug resistance in M tuberculosis.

The scientists analyzed M tuberculosis genomes from 252 patients in the largest outbreak to date of MDR-TB in South America. The isolates were collected from patients with known HIV status between the mid-1990s and 2009.

The team was able to identify the mutations that enable the bacteria to resist antibiotics, according to an eLife summary of the report. Using a mathematical model to reconstruct the spread of MDR-TB during the outbreak also made it possible to assess who transmitted TB to whom.

The researchers then combined the results of both methods to estimate the length of the TB latency period—the time from infection to infectiousness—and identify patients in whom TB strains evolved resistance mutations, according to an eLife press release.

"The results suggest that M. tuberculosis does not evolve drug resistance any faster in patients with HIV than otherwise," the report summary states. "Furthermore, patients infected with both HIV and tuberculosis did not transmit tuberculosis to others more often than patients who did not have HIV. However, being infected with HIV did increase the likelihood that an individual would contract tuberculosis." HIV also speeded the progression of patients' TB symptoms.

In the press release, the authors observed that HIV provides TB with a pool of susceptible hosts, increasing the rate of co-infection. They said this explains why HIV patients at a major hospital in Buenos Aires, Argentina, played a central role in fueling South America's largest MDR-TB epidemic in the early 1990s.
Aug 9 eLife report
Aug 9 eLife
press release

 

Flu patterns vary as Southern Hemisphere flu season progresses

The Southern Hemisphere's flu still reflects a mixed picture in different parts of the region, with rising activity in southern Africa and some South American locations, but lower than expected levels in countries like Australia and New Zealand, the World Health Organization (WHO) said yesterday in its latest update.

Flu markers increased in Chile and appear to have plateaued in Paraguay, both of which are seeing cocirculation of 2009 H1N1 and influenza B viruses, according to the WHO. In tropical parts of South America, where severe disease was higher compared to last season, flu is declining in most countries.

In southern Africa, the flu rise involves a shift from influenza B to H3N2.

Flu activity in Australia increased a bit, and H3N2 is the predominant strain. In New Zealand, flu activity is still low for this time of year.

In the Caribbean and Central American regions, flu continued at low levels, and what little flu activity that is occurring in other parts of the world is generally led by influenza B.

Globally, nearly 65% of positive flu viruses were influenza A. Of the subtyped samples, 50.3% were 2009 H1N1 and 49.7% were H3N2, the WHO said.
Aug 8 WHO global flu update

 

Campylobacter linked to growth restriction in kids

Campylobacter infection is a common cause of diarrhea and intestinal inflammation in children, leading to dehydration and illness. A new study in Clinical Infectious Diseases now shows infection with the bacterium also leads to impaired growth between the ages of 0 and 2.

Researchers sampled stools from 1,892 children from eight sites in South America, sub Saharan Africa, and Asia, and found most (84.9%) had Campylobacter positive stool samples before 1 year of age. Campylobacter infection was associated with lower length-for-age at 24 months. Infection with the bacteria between the ages of 6 to 12 months was associated with the most growth limitation.

The authors also said that in children with Campylobacter infection, duration of breastfeeding was short (3.2 months), and treated water sources was sporadic.

"Promotion of exclusive breastfeeding, drinking water treatment, improved latrines, and targeted

antibiotic treatment may reduce the burden of Campylobacter infection and improve growth in children in these settings," the authors concluded.

Campylobacter is endemic in low-resource settings, the authors said, while in high-resource settings the bacteria are most commonly linked to undercooked and raw poultry.
Aug 9 Clin Infect Dis study

 

Chikungunya infects 617 more in the Americas

The Pan American Health Organization (PAHO) recently reported 617 more suspected or confirmed chikungunya cases, lifting the total in the Americas since the first of the year to 215,164.

The weekly increase was smaller than previous weeks, and several countries didn't report new cases. For example, the rise in PAHO's previous report was 1,708 new cases.

The largest portion of the newly reported cases were from El Salvador and the Dominican Republic, which reported in for the first time this year with 112 cases. Other countries reporting additional cases were Costa Rica, Ecuador, and Mexico.

One more death from the virus was reported, putting that number at 29 so far for the year.

The Americas' chikungunya outbreak began in December 2013 on St. Martin in the Caribbean.
 Aug 5 PAHO update

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