Early hospital admittance, antiviral treatment credited with boosting H1N1 survival rate

Arizona State University mathematical epidemiologist Gerardo Chowell-Puente recently led a team of U.S. and Mexican researchers in examining the 2009 H1N1 mortality rate in Mexico.

The findings, which appeared in the April 20 online publication of BMC Infectious Diseases, were reported on April 23 by the Center for Infectious Disease Research & Policy News.

Key discoveries were that delayed hospitalization increased the risk of death nearly threefold, and administration of antiviral therapy almost halved the risk.

The research team used data from a surveillance system created by the Mexican Institute for Social Security for the purpose of tracking the 2009 pandemic.

The strongest factor for death of confirmed H1N1 patients was found to be delayed hospitalizations, with a case-fatality rate of 23.3 percent for those admitted more than two days following the onset of symptoms. Comparatively, the rate was eight percent for those admitted within two days of the onset of symptoms.

During the spring wave, Tamiful or Relenza was recommended to all clinic or hospital patients with influenza-like illness and severe symptoms or those with mild symptoms in high-risk groups.

Use of the antivirals dropped from 48.6 percent of confirmed cases in the spring wave to only 8.7 percent in the fall wave.

The case-fatality rate during the spring was 4.6% and fell to 0.7 percent in the summer. However, it jumped to 2.5 percent in the fall wave, when the use of antivirals was low.

According to the report, the drop in antiviral use during the fall may have been attributed to conservative administration of the drugs when the perceived severity of the pandemic diminished.

Chowell-Puente, an assistant professor in the School of Human Evolution and Social Change in the College of Liberal Arts and Sciences, looks at the connection of mathematical and computational models to real epidemic scenarios to make inferences on transmission dynamics and the effects of public health intervention strategies.