Infectious Diseases News Brief - December 4, 2009

[Current Issue -Table of contents]

Flu and Children: RSV Causes Far More Hospitalizations Than Seasonal Flu

Influenza, particularly H1N1, has understandably captured the attention of public health officials, the media and the public. However, an analysis from Children's Hospital Boston, based on patients seen in its emergency department (ED) during several recent flu seasons, shows that another virus -- respiratory syncytial virus (RSV) -- takes a substantially greater disease toll among young children than does seasonal flu. According to the CDC, RSV is the most common cause of bronchiolitis and pneumonia in children under 1 year of age in the U.S. RSV-related illnesses were also twice as likely to lead to additional primary care clinic visits and to antibiotic treatment. The parents of children with RSV missed almost three times more workdays than parents of children with the flu, and parents of children under age 2 were nearly five times more likely to miss work when their child had RSV. Bourgeois and colleagues [the researchers] prospectively studied children aged 7 and under visiting the Children's Hospital Boston ED with acute respiratory illnesses during five consecutive seasons (2001-2006) -- an average of 5,288 visits each year. A subgroup of children underwent viral testing; 23.6 percent were found to have RSV and 11.2 percent had influenza. Using census data and data on pediatric acute respiratory illness from the National Hospital and Ambulatory Medical Care Survey, Bourgeois and colleagues were able to extrapolate their data nationally and determine population-based rates of RSV and flu illnesses. They estimate that 21.5 ED visits per 1,000 children were attributable to RSV, as compared with 10.2 per 1,000 for seasonal flu. Children under age 2 with RSV had the most visits -- 64.4 per 1,000. Estimated hospitalization rates were 8.5 per 1000 for RSV, versus 1.4 per 1000 for flu. Nationally, caregivers missed an estimated 716,404 workdays each year for RSV and 246,965 for flu. Although the study only looked at children age 7 and younger, the researchers believe their findings are relevant to older age groups, since young children drive transmission of viral infections, the researchers say.

Source: Science Daily November 25, 2009
http://www.sciencedaily.com/releases/2009/11/091123114642.htm

Measuring and Modeling Blood Flow in Malaria

When people have malaria, they are infected with Plasmodium parasites, which enter the body from the saliva of a mosquito, infect cells in the liver, and then spread to red blood cells. Inside the blood cells, the parasites replicate and also begin to expose adhesive proteins on the cell surface that change the physical nature of the cells in the bloodstream. Experiments show that infected red blood cells are stiffer and stickier than normal ones -- in the later stages of the disease, up to 10 times stiffer. They also tend to adhere to the endothelial cells lining the vasculature, affecting the normal blood flow. This explains some of the common symptoms of malaria, such as anemia and joint pain. Doctoral student Dmitry Fedosov and Brown University professor George Karniadakis are studying how malaria infections affect the physical properties of red blood cells, and alter normal blood flow circulation. In particular, they examine an increase in blood flow resistance, and dynamics of infected cells in the bloodstream. They also monitor the mechanical properties of infected red blood cells by measuring membrane temperature fluctuations, and through the response of a "microbead" that is attached to the cell and twisted. The measured properties are then used in modeling the flow of red blood cells in people infected with malaria. They also collaborate with the group of professor Subra Suresh at MIT, who obtain experimental measurements of the properties and the flow of healthy and infected cells. Recently they found that temperature fluctuations of infected red blood cell membranes measured in experiments are not directly correlated with the reported cell properties, hence suggesting significant influence of metabolic processes. They measured an increase in resistance to blood flow in the capillaries and small arterioles during the course of malaria and found that parasitized red blood cells have a "flipping" motion at the vessel wall that appears to be due to stiffness of the infected cells. The developed models will aid to make realistic predictions of the possible course of the disease, and enhance current malaria treatments.

Source:Science Daily November 22, 2009
http://www.sciencedaily.com/releases/2009/11/091123083700.htm

MRSA Entering US Hospitals Via Outpatients Is On The Increase

A new study suggests that community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is on the rise in US hospitals, and is adding to rather than replacing the type of MRSA that arises within hospitals, the hospital-associated MRSA (HA-MRSA); the study authors also found that the entry route for CA-MRSA is via outpatients who pick up the infection in places like gyms, schools and other public places. For the study, Laxminarayan and colleagues analyzed data from more than 300 microbiology labs used by hospitals all over the US and found that between 1999 and 2006 there was a seven-fold rise in the proportion of "community-associated" strains of MRSA in hospital outpatient units. Since doctors and patients often move between inpatient and outpatient units, this rise in outpatient MRSA is a significant threat to patient safety in hospitals, suggested the researchers. In summary, the results of the study are presented: from 1999 to 2006, the proportion of outpatients with staph who were infected with MRSA went up more than 90 per cent; this MRSA infected population now accounts for more than 50 per cent of all staph infections; it is likely that the rise in MRSA infections in almost entirely due to CA-MRSA; CA-MRSA rose from 3.6 per cent of all MRSA infections in 1999 to 28.2 per cent in 2006, a seven-fold increase; and, similar increases in inpatients suggest that these strains are spreading rapidly in hospitals as well. The MRSA "superbug" is a deadly infection-causing bacteria that has become resistant to most common antibiotics; the community-associated strain now poses a far greater threat to health than ever before, and it is making its way into hospitals, said the authors. MRSA attacks wounds and can trigger potentially fatal blood infections. Although CA-MRSA tends to be less virulent and is generally more treatable with antibiotics, it can still cause significant illness and deaths. About 20,000 people in the US die every year from MRSA and there are more than 63,000 deaths each year linked to hospital acquired infections that are resistant to at least one antibiotic: this is more deaths than from AIDS, traffic accidents or flu.

Source: Medical News Today November 25, 2009
http://www.medicalnewstoday.com/articles/172102.php