News Scan for Oct 26, 2015

More chikungunya cases
;
Tick-borne misdiagnosis
;
Potential RSV drug
;
WHO on polio-free Nigeria

Chikungunya outbreak in Americas tops 600,000 cases this year

The Pan American Health Organization (PAHO) on Oct 23 reported 2,095 new cases of chikungunya in the Caribbean and Americas.

This brings the overall total this year to 600,553, including 575,281 suspected, 24,388 confirmed locally acquired, and 884 imported cases. PAHO's last update included 2,464 new cases.

Colombia continues to report high case numbers, with 1,207 new cases last week; its 2015 outbreak total now stands at 340,988.

Mexico, which has experienced small increases in confirmed chikungunya cases over the last several weeks, reported 365 new cases, bringing its outbreak total this year to 8,688. Ecuador reported 368 new cases last week, bringing its 2015 total to 33,414.

No new deaths were reported in the most recent PAHO update, keeping the fatality total for the year at 63.

The chikungunya epidemic began in December 2013 with the first locally acquired chikungunya case ever reported in the Americas, on St. Martin in the Caribbean. Since then, PAHO has reported 1,747,322 cases.
Oct 23 PAHO update

 

Benign rickettsiosis likely misdiagnosed as Rocky Mountain spotted fever

Increasing reports of Rocky Mountain spotted fever unassociated with high hospitalization and death rates are likely due to fairly benign spotted fevers carried by the lone star tick, according to findings today in the American Journal of Tropical Medicine and Hygiene.

Researchers from the Centers for Disease Control and Prevention (CDC) evaluated reports of Rocky Mountain spotted fever in the United States from 1981 to 2013, associated hospitalization and case-fatality rates, and expansion of Amblyomma americanum's (the lone star tick's) geographic range.

Reports of Rocky Mountain spotted fever (Rickettsia rickettsii) increased from 1.7 to 14.3 cases per million from 2000 to 2012, while the associated death rate decreased from around 2% in the 1990s to less than 1% for 12 consecutive years after the turn of the millenium.

R rickettsii typically causes high fever, rash, and internal bleeding; infection is fatal in 20% to 25% of cases untreated by doxycycline within 5 days. The infection is spread by the American dog tick, the Rocky Mountain wood tick, and the brown dog tick. Infections caused by R ambylommii, which is carried by the lone star tick, may be asymptomatic or cause a mild fever, though it is serologically indistinguishable from R rickettsiii.

During the 1990s, researchers saw a fairly low R rickettsii infection rate (1.68 cases per million) accompanied by a high death rate (2.03%) as expected with Rocky Mountain spotted fever. In the 2010s, however, the infection rate climbed to 10.0 cases per million, while the death rate plummeted to 0.47%.

Many new cases reported as Rocky Mountain spotted fever were likely infections caused by R ambylommii, carried by the lone star tick as its range expanded north and west over the past decade, the authors wrote. Rickettsiosis that is caused by bites from the Gulf Coast tick and is a more serious disease yet has a low death rate may also have been misdiagnosed as Rocky Mountain spotted fever, the researchers said.

Up to half of all lone star ticks may carry R ambylommii, while less than 1% of American dog ticks carry R rickettsii. Investigators said that reports of true outbreaks of Rocky Mountain spotted fever are likely due to better reporting and enhanced clinician awareness of the disease.
Oct 26 Am J Trop Med Hyg study

 

Motavizumab prevents RSV-related hospitalizations in infants

Administering the monoclonal antibody motavizumab to healthy infants led to a decrease in hospitalization for acute lower respiratory tract infections caused by respiratory syncytial virus (RSV), according to findings yesterday in The Lancet Infectious Diseases.

Researchers from MedImmune and the Center for American Indian Health at the Johns Hopkins University Bloomberg School of Public Health in Baltimore conducted a phase 3, double-blind, placebo-controlled, randomized clinical trial of motavizumab from 2004 to 2007 among Native American infants on the Navajo Nation and two southwestern Apache reservations. All 2,127 infants included in the study were born at 36 weeks' gestational age.

Of the 1,417 infants who received five monthly doses of motavizumab from October to December each year, 21 (2%) were hospitalized with RSV, compared with 80 (11%) of 710 infants in the placebo group. Motavizumab led to an 87% reduction in the risk of hospitalization due to RSV (relative risk, 0.13; 95% confidence interval, 0.08-0.21).

A higher rate of serious adverse events were reported in the placebo group (148, or 21%) than in the treatment group (212, or 15%). More hypersensitivity events such as skin reactions occurred in the motavizumab group (208, or 14.7%) than in the placebo group (87, or 12.3%).

Six deaths occurred in infants enrolled in the study, four of which were in infants assigned to the motavizumab group. None of the deaths were related to the study or RSV infection, the researchers said.

Investigators monitored infants for medically attended wheezing until they turned three and found similar rates of wheezing in the motavizumab group and the placebo group. The study was funded by MedImmune, which produces motavizumab.
Oct 25 Lancet Infect Dis
study

 

WHO ceremony confirms Nigeria now officially off polio-endemic list

At a ceremony today in Nigeria, a World Health Organization (WHO) spokesperson formally removed Nigeria from the list of countries where polio remains endemic, meaning that only Afghanistan and Pakistan remain and that global polio eradication is a step closer.

Nigeria has not seen a case of wild poliovirus infection for 15 months, which is more than the target period for disease interruption. The WHO first announced that Nigeria had reached this milestone on Sep 25.

"The remarkable achievement is a true testament of what political will, government leadership, community ownership, and the collective efforts of partners can achieve when united behind a global public health good," said Dr Matshidiso Moeti, WHO regional director for Africa, at the ceremony today. He added this caution: "To achieve polio eradication, we must ensure that in the next two years no child is paralyzed due to polio. There is no time for complacency and we must remain vigilant."

In 1988 polio was considered endemic in more than 125 countries, says a WHO press release today. And a release Sep 25 said that as recently as 2012, Nigeria accounted for more than half the polio cases worldwide.

Moeti gave much credit for Nigeria's achievement to those on the frontlines, saying, "Health care workers, community mobilizers, religious and traditional leaders have been the real unsung heroes in helping to reach every last child with life-saving polio vaccine."

Significant contributions were made as well by WHO, development partners, and the Global Polio Eradication Initiative. Immunization campaigns are already planned for December and 2016.
Oct 26 WHO press release
Sep 25 WHO press release

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