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Notebook Science

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‘Herd immunity’ hurdle

Mass immunizations against Ebola offer little promise of success

On the heels of the World Health Organization’s announcement of an Ebola outbreak in the Democratic Republic of Congo, a new research study cast doubt on the ability of mass vaccination campaigns to prevent such Ebola outbreaks in the future.

Since April, Congo’s Équateur province has reported 49 likely Ebola cases, including 27 deaths and 28 confirmed cases as of May 22. With memories of the West Africa Ebola epidemic that claimed the lives of 11,310 people a few years ago, WHO has shipped several thousand doses of an experimental vaccine into Congo, meant for health workers and anyone else in immediate contact with Ebola patients.

A larger, mass vaccination campaign to prevent widespread transmission would likely be ineffective, according to the study conducted by England’s University of Kent and published May 9 in Frontiers in Immunology.

Each Ebola patient, on average, infects at least four people in the early stages of the disease. According to the researchers’ analysis, the rapid spread of the virus means 80 percent of the population would need immunization to achieve “herd immunity” and prevent widespread transmission, likely an unachievable number.

In a vaccination trial during the 2014 Ebola outbreak, health professionals could vaccinate only 49 percent of the contacts of infected individuals. Thirty-four percent refused vaccination, and health issues such as HIV and cancer prevented many others from receiving immunization.

To date, no FDA-approved Ebola vaccine exists, and none of the experimental vaccines offer protection against all four types of life-threatening Ebola viruses. Furthermore, researchers do not know if the current vaccines can provide the long-term protection needed to defend against a virus with which humans repeatedly come into contact through animals.

Vaccination campaigns in rural areas of countries like Congo are difficult due to transportation problems, lack of equipment and trained medical personnel, and cultural and language barriers.

The researchers concluded that targeted immunization programs—focused exclusively on healthcare workers and other contacts of infected persons—remain the best vaccine strategy against Ebola for now.

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Centers for Disease Control and Prevention

(Centers for Disease Control and Prevention)


Cracking the bacteria

A weak spot in a bacterial protein could be key to killing superbugs 

Antibiotic-resistant bacteria pose an ever-growing global threat, currently claiming the lives of at least 23,000 people in the United States each year. Research published this year shows that certain strains of a deadly, multidrug-resistant bacterium have now developed resistance to the last-resort antibiotic colistin.

That’s worrisome news, but scientists at Harvard University have discovered a weakness in the protective covering of most bacteria that could offer a glimmer of hope in the battle against superbugs.

A shell, or wall, that encapsulates bacteria serves to keep them structurally intact and safe from toxins, drugs, and viruses that could kill them. Many current antibiotics work by disrupting the proteins that build this protective shield, but superbug proteins have adapted and many of those drugs can no longer stop the shell-building process.

In the study published in the April 5 issue of Nature, the Harvard research team discovered a weak spot—an externally accessible, pocketlike cavity—in RodA, a wall-building protein present in almost all bacteria.

When the researchers mildly altered these pockets in two of the most common disease-producing bacteria, RodA became disabled and the bacterial cells burst.

If scientists can develop new drugs that bind to these pockets, they would disable the protein in the same way. “That would, in essence, crack the wall, weaken the cell and set off a cascade that eventually causes it to die,” David Rudner, co-leader of the study, said in a statement.

Because most bacterial species contain RodA, a drug made to disrupt the protein should work against many different kinds of harmful bacteria.

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(Peter Reid/NASA) ()


Earth on decline

The planet’s magnetic field fluctuates but continues to weaken

The strength of Earth’s magnetic field has been weakening for 160 years, and some scientists worry the planet’s magnetic poles may soon flip or reverse. In a recent study, researchers from New York’s University of Rochester analyzed data from as far back as the first millennium A.D. to try to understand better the magnetic field decay. They discovered a pattern of fluctuations in magnetic field direction and intensity but said it is too early to know if a full-blown pole reversal is on the horizon.

Swirling liquid iron in the Earth’s outer core generates the magnetic field that encases our planet and protects us from harmful solar radiation. If the field becomes too weak, increased radiation levels could cause increases in skin cancer.

Many scientists believe the last pole reversal took place nearly 800,000 years ago. A modern-day reversal could cause electrical grid failures and wreak havoc on navigational systems and satellites.

The weakest region in the magnetic field encompasses a large area that stretches from Chile to Zimbabwe. The University of Rochester scientists believe the birthplace of pole reversals may lie in an exceptionally dense area 1,800 miles beneath Southern Africa. This area, positioned just above the boundary between the Earth’s hot liquid outer core and the more solid, cooler mantle, may periodically sink slightly, disrupting the flow of iron and decreasing the magnetic field, the scientists said. In their research, published in Geophysical Research Letters in January, they studied magnetic minerals in African clay samples and identified a series of field fluctuations dating back to A.D. 400.

David Coppedge, a young-earth creationist and founder of the Creation-Evolution Headlines blog, believes the magnetic field will continue to decay. He noted on his website that while currents in the Earth’s core can act as a dynamo and generate a magnetic field, those currents will eventually slow down without an energy source. Coppedge suggested the magnetic field is sustained by dying residual currents formed when God first created the Earth.

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