The unwelcome news in the midst of bad flu season is that influenza spreads easier than previously thought, possibly in the very breath you take.
The upshot from a new study1 is that a virus thought to be spread primarily by coughing and sneezing needs neither to transmit from person to person. Rather, it can be airborne and transmitted in the normal, exhaled breaths of an infected person, researchers reported.
The authors could not be reached for comment as this issue went to press, but concluded the following in the paper:
“We recovered infectious influenza virus from 52 samples of fine aerosols collected from exhaled breath and spontaneous coughs produced by 142 cases of symptomatic influenza infection during 218 clinic visits,” they reported. “Finding infectious virus in 39% of fine-aerosol samples collected during 30 minutes of normal tidal breathing in a large community-based study of confirmed influenza infection clearly establishes that a significant fraction of influenza cases routinely shed infectious virus, not merely detectable RNA, into aerosol particles small enough to remain suspended in air and present a risk for airborne transmission.”
As this issue went to press, hospitals and communities in the U.S. were being hard hit with influenza, making it important to ensure healthcare workers are vaccinated as the seasonal epidemic peaks.
The predominant strain of H3N2 influenza A is not well matched by the vaccine this year, but immunization still can lessen the severity of illness. Antivirals administered as soon as possible after infection are proving effective, CDC officials note.
“Our information so far suggests that vaccine effectiveness against the predominant H3 viruses will probably be somewhere around what we saw in the 2016-2017 season, which was in the 30% range,” CDC epidemiologist Dan Jernigan, MD, said at a recent press conference. “While this is better than the 10% that has been reported from Australia in one study, it still leaves a lot to be desired.”
Thirty Children Die of Flu
As of Jan. 13, 2018, the CDC was reporting that all U.S. states but Hawaii were reporting widespread flu activity, with “high” influenza activity reported in 32 states, New York City, and Puerto Rico. At least 30 children have died of influenza infection.
“Many people have been following anecdotes and reports in the media of young, otherwise healthy adults who have been admitted with very progressive influenza disease, then died because of that,” Jernigan said. “Reports are out there. It’s just a reminder that flu, while causing mild disease in a lot of people, can also cause severe disease and death in others.”
The highest hospitalization rates were among people 65 years and older (136.5 per 100,000), followed by adults aged 50-64 years (33.2 per 100,000), and children younger than five years (22.8 per 100,000). The CDC has tested 168 influenza A(H1N1), 587 influenza A(H3N2), and 209 influenza B viruses for resistance to antiviral medications (i.e. oseltamivir, zanamivir, or peramivir). While the majority of the tested viruses showed susceptibility to the antiviral drugs, two (1.2%) H1N1pdm09 viruses were resistant to both oseltamivir and peramivir, but were sensitive to zanamivir, the CDC reported.
“I think the simplest way to describe it is that flu is everywhere in the U.S. right now,” Jernigan said. “Our team that does this kind of surveillance has been doing this for 13 years, and this is the first year we had the entire continental U.S. [with] widespread activity.”
CDC recommends that people at high risk for serious flu complications should be treated as soon as possible with antiviral drugs if they have flu-like symptoms.
“That means people that are 65 and older, young children, people with chronic conditions like diabetes, heart disease, or asthma,” Jernigan said. “It means pregnant women and others more vulnerable to serious flu illness. Clinicians should not wait for confirmed [flu test results].”
1. Yan J, Grantham M, Pantelic J, et al. Infectious virus in exhaled breath of symptomatic seasonal influenza cases from a college community. Proc Nat Acad Sci USA Dec. 15, 2017: Early Edition:doi:10.1073/pnas.1716561115.