Humidity as a non-pharmaceutical intervention for influenza A

Abstract

Influenza is a global problem infecting 5–10% of adults and 20–30% of children annually. Non-pharmaceutical interventions (NPIs) are attractive approaches to complement vaccination in the prevention and reduction of influenza. Strong cyclical reduction of absolute humidity has been associated with influenza outbreaks in temperate climates. This study tested the hypothesis that raising absolute humidity above seasonal lows would impact influenza virus survival and transmission in a key source of influenza virus distribution, a community school. Air samples and objects handled by students (e.g. blocks and markers) were collected from preschool classrooms. All samples were processed and PCR used to determine the presence of influenza virus and its amount. Additionally samples were tested for their ability to infect cells in cultures. We observed a significant reduction (p < 0.05) in the total number of influenza A virus positive samples (air and fomite) and viral genome copies upon humidification as compared to control rooms. This suggests the future potential of artificial humidification as a possible strategy to control influenza outbreaks in temperate climates. There were 2.3 times as many ILI cases in the control rooms compared to the humidified rooms, and whether there is a causal relationship, and its direction between the number of cases and levels of influenza virus in the rooms is not known. Additional research is required, but this is the first prospective study suggesting that exogenous humidification could serve as a scalable NPI for influenza or other viral outbreaks.

High Prevalence of Viral Infections Among Hospitalized Pneumonia Patients in Equatorial Sarawak, Malaysia

“…A drier season typically falls between May and September, with June to August seeing the least rain. Our [15,16]. Our findings regarding the prevalence of RSV support the existing literature that the 2 antigenic subgroups A and B can cocirculate but typically differ by season [17].…”

Nonpharmaceutical Measures for Pandemic Influenza in Nonhealthcare Settings—Personal Protective and Environmental Measures

“…In this review, we focused on 3 personal protective measures and 1 environmental measure. Other potential environmental measures include humidification in dry environments (48), increasing ventilation (49), and use of upper-room UV light (50), but there is limited evidence to support these measures. Further investigations on the effectiveness of respiratory etiquette and surface cleaning through conducting RCTs would be helpful to provide evidence with higher quality; evaluation of the effectiveness of these measures targeting specific population groups, such as immunocompromised persons, would also be beneficial ( Table 2).…”

Seasonality of Respiratory Viral Infections

“…Such interventions with humidifiers have been realized since the 1960s with promising results (122)(123)(124)(125)(126)(127). More recently, a study in Minnesota found that humidifying preschool classrooms during January to March to ∼45% RH results in a significant reduction in the total number of influenza virus and viral genome copies found in the air and on objects compared to control classrooms (128). Such nonpharmaceutical interventions can be combined with vaccination strategies to achieve better prevention of respiratory viral infections ( Table 2).…”