The top posts of 2007: number 7

Over the holiday period, the physics arxiv blog is re-running the most popular blogs (by page views) of 2007.

The frightening prospect of flu
23 November

Flu transmission

Bird flu may get all the headlines but the number of deaths it causes each year is currently measured in hundreds. The real killer, the one that should set yer spine a-shiver, is ordinary fly which kills hundreds of thousands each year.

With winter nearly upon us up here in the northern hemisphere, the spectre that we’ll be a-shakin and a-sweatin our way through a flu pandemic in the coming months is raising its ugly head again.

So what can science tell us about the way pandemics spread? Not enough, according to Gerardo Chowell from Arizona State University in the US and his friend Hiroshi. They’ve posted a comprehensive review of epidemic science dating back to the 1918 Spanish flu epidemic that killed as many as 100 million people by some estimates. We’ve learnt an awful lot since then about the way flu spreads but the frightening thing about Gerardo’s review is how much more we need to understand.

It’s not just small things that are up in the air but sizable pieces of the jigsaw. We still don’t know some basic probabilities associated with infection. For instance, given that an individual is infected with flu, what are the chances that the disease will manifest itself clinically? And given that the disease has manifested itself clinically in an individual, what are the chances of that person dying. And if a virus can be caught from a number of diffferent host species (as it might eventually be with bird flu) what is the probability of transmission?

Without a good understanding of these kindsa factors, it’s gonna be difficult for authorities to plan an effective response to a flu pandemic.

Mah advice? Stock up on food and water.

Ref: Quantifying the Transmission Potential of Pandemic Influenza

One Response to “The top posts of 2007: number 7”

  1. H5N1 avian flu: Spread by drinking water into small cluster

    Human to human and contact transmission of influenza occur – but are overvalued immense. In the course of Influenza epidemics in Germany recognized cluster are rarely (9% of the cases in the season 2005).
    In temperate climates the lethal H5N1 avian flu virus will be transferred to humans strong seasonal in the cold via cold drinking water, as with the birds feb/mar 2006.
    Recent research must worry: So far the virus had to reach the bronchi and the lungs in order to infect humans. Now it infects the upper respiratory system (mucous membranes of the throat e.g. when drinking and mucous membranes of the nose and probably also the conjunctiva of the eyes as well as the eardrum e.g. at showering). In a few cases (Viet Nam, Thailand) stomach and intestine by the H5N1 virus were stricken but not the bronchi and the lungs. The virus might been orally taken up, e.g. when drinking contaminated water.
    The performance to eliminate viruses of the drinking water processing plants in Germany regularly does not meet the requirements of the WHO and the USA/USEPA. Conventional disinfection procedures are poor, because microorganisms in the water are not in suspension, but embedded in particles. Even ground water used for drinking water is not free from viruses.
    In temperate climates the strong seasonal waterborne infections like norovirus, rotavirus, salmonellae, campylobacter and – differing from the usual dogma – influenza are mainly triggered by drinking water dependent on the drinking water temperature (in Germany minimum feb/mar – maximum august). There is no evidence that influenza primary is transmitted by saliva droplets. In temperate climates the strong interdependence between influenza infections and environmental temperatures can’t be explained with the primary biotic transmission by saliva droplets from human to human with temperatures of 37.5°C. There must be an abiotic vehicle like cold drinking water. There is no other appropriate abiotic vehicle. In Germany about 98% of inhabitants have a central public water supply with older and better protected water. Therefore in Germany cold water is decisive to virulence of viruses.
    In hot climates/tropics the flood-related influenza is typical after extreme weather and natural after floods. Virulence of Influenza virus depends on temperature and time. If young and fresh H5N1 contaminated water from low local wells, cisterns, tanks, rain barrels or rice fields is used for water supply water temperature for infection may be higher as in temperate climates.

    Dipl.-Ing. Wilfried Soddemann
    Epidemiological Analysis: