Adults with obesity are more susceptible to influenza A/H1N1pdm, also known as the swine flu virus, according to a new study.
The study did not, however, show a similar association with seasonal flu.
The results could be relevant in understanding how infectious diseases such as influenza or the ongoing coronavirus pandemic might affect different segments of the population, the researchers say.
“This research is important because obesity around the whole world is increasing rapidly. It’s approximately tripled since the ’70s,” says Hannah Maier, a postdoctoral fellow at the University of Michigan School of Public Health and first author of the study in the journal Clinical Infectious Diseases.
“We’re having a lot more obesity, right now we’re dealing with the pandemic, and it was just announced that there might be another potential swine flu pandemic. If obesity is associated with increased risk and there’s a lot more obesity, that could mean a lot more infections.”
Maier and colleagues looked at data from more than 1,500 individuals in 330 households enrolled in the Nicaraguan Household Transmission Study, an ongoing community-based study tracking the health of a community in Managua, Nicaragua. Researchers followed study participants 10-15 days, conducting swab tests and blood tests to confirm infection.
The researchers found that adults with obesity had twice the odds of symptomatic H1N1 infection compared to those without obesity. Researchers did not see the association with the H3N2 seasonal influenza strain.
While researchers don’t yet know the mechanism linking obesity to increased disease severity, chronic inflammation increases with age and is associated with chronic diseases. Separate studies have shown that obesity increases proinflammatory and decreases anti-inflammatory cytokine levels, the researchers say.
Obesity can also impair wound healing and lead to mechanical difficulties in breathing and increased oxygen requirements.
In 2009, a strain of flu affecting pigs jumped to humans. This virus, H1N1pdm, infected many people around the world.
A new study released last month showed that a new strain of H1N1 in swine in China has the potential to become a pandemic, which highlights the importance of continuing this type of research even while facing the coronavirus pandemic, says senior author Aubree Gordon, an epidemiologist at the School of Public Health.
“This underscores that although we are in the middle of a pandemic, we cannot stop being vigilant for the emergence of other viruses, particularly influenza,” Gordon says.
“In addition, this highlights that the US needs to participate in the World Health Organization. The WHO influenza program provides a critical service to the world monitoring influenza circulation to make vaccine strain recommendations and surveilling for potential emergence of new influenza viruses.”
Additional coauthors are from the University of Michigan; the Sustainable Sciences Institute in Managua, the Ministry of Health in Managua; and the University of California, Berkeley. The National Institute for Allergy and Infectious Disease supported the work.
Source: University of Michigan