Do humidifiers help cure the flu?

Question

According to this report, absolute humidity affects transmission and survival of the influenza virus with 90% accuracy. Lower humidity at winter promotes both the influenza virus transmission and its survival.

Is there any evidence that increasing humidity levels positively affects the prognosis of someone who's already been infected with the virus (i.e, either shortens the duration or diminishes the severity of the illness, not including obvious symptoms such as easing congestion etc)?

The only reason to believe this might be true is that higher humidity levels might also increase moisture in the nasal cavity thus weakening the virus but this is just a theory.

Does anyone have concrete data on this subject?

Answer 1

There is a mixed, but largely unconvincing evidence that increased moisture within the nose would help to prevent or cure flu or common cold.

Common colds: Relief for a stuffy nose, cough and sore throat (Informed Health Online):

Many people find it pleasant to breathe in (inhale) steam ...But this kind of inhalation doesn't have a clear effect on cold symptoms.

Dehydration can make your nasal mucosa dry, but:

Drinking a lot of fluids is also often recommended if you have a cold. There's no scientific proof that this will help, though.

In one 2008 study in 401 children 6-10 years old, nasal irrigation with saline solution decreased and shortened symptoms in some children with common cold or flu. But in several similar studies, nasal irrigation had no effect.

Important to know: Even antiviral drugs can effectively shorten the duration of flu when taken within 24-48 hour after the onset of symptoms (CDC.gov). This also likely applies for any nasal moisturizer, because viruses act within the cells, where can't be reached by drugs or moisture.