A study in Mexico confirms that younger people are more susceptible to contracting H1N1 influenza than are children and the elderly.

Via MedPage Today:

The majority of confirmed infections (56 percent) occurred in individuals 10 to 39 years old, with only 10.2 percent occurring in people 40 and older, according to Victor Borja-Aburto, PhD, of the Mexican Institute for Social Security in Mexico City, and colleagues.

“The high incidence of infection in young people could show not only their different exposure related to their daily activities but also that people older than 60 years might have some immunity against the H1N1 virus,” they wrote online in The Lancet.

However, the death rate was highest among those 70 and older, at 10.3 percent. The death rate was 2 percent or less for all age groups younger than 40.

The findings are consistent with previous epidemiological studies of the ongoing pandemic.

In the Lancet, the researchers addressed doubts in the research community about the severity of the pandemic as it continues to play out:

Some researchers believe, with the information available up to now, that the present H1N1 influenza virus will not cause a pandemic on the scale of those during the 20th century. This pandemic might not be the one we expected; however, the virus is evolving and the threat continues.

Primary source: The Lancet
Source reference:
Echevarría-Zuno S, et al “Infection and death from influenza A H1N1 virus in Mexico: A retrospective analysis” Lancet 2009; DOI: 10.1016/S0140-6736(09)61638-X.

Additional source: The Lancet

Source reference:
Laguna-Torres V, Gomez Benavides J “Infection and death from influenza A H1N1 virus in Mexico” Lancet 2009; DOI: 10.1016/S0140-6736(09)61916-4.