Shouldn't we all be immune to West Nile soon?

[myrnajean]

I mean, it’s a virus right? I always thought once you had a virus, like chicken pox for instance, you never got it again.
With all the mosquitos all over the place, it seems that eventually, everyone will get bit, those with weakened immune systems will get sick and maybe die, but the rest of us should become immune to it.
From what I understand, most people who get WN don’t even necessarily exhibit symptoms. So, am I missing something?

[Colibri]

Yes, that most people never get West Nile.

[myrnajean]

Ah yes, but those that do, are they immune or not?

[John_Mace]

From the CDC Q&A sheet:

Q. How long does the West Nile virus remain in a person’s body after they are infected?
A. There is no scientific evidence indicating that people can be chronically infected with West Nile virus. What remain in a person’s body for long periods of time are antibodies and “memory” white blood cells (T-lymphocytes) that the body produces to the virus. These antibodies and T-lymphocytes last for years, and may last for the rest of a person’s life. Antibodies are what many diagnostic tests look for when clinical laboratories testing is performed. Both antibodies and “memory” T-lymphocytes provide future protection from the virus.

[John_Mace]

The other thing to remember about WNV is that although it can be fatal to a small percentage of those infected (< 1%), most people who are infected don’t exhibit any symptons at all ( ~ 80%). So, almost everyone is already “immune”.

[Colibri]

From here

Q. How long does the West Nile virus remain in a person’s body after they are infected?
A. There is no scientific evidence indicating that people can be chronically infected with West Nile virus. What remain in a person’s body for long periods of time are antibodies and “memory” white blood cells (T-lymphocytes) that the body produces to the virus. These antibodies and T-lymphocytes last for years, and may last for the rest of a person’s life. Antibodies are what many diagnostic tests look for when clinical laboratories testing is performed. Both antibodies and “memory” T-lymphocytes provide future protection from the virus.

Q. If a person contracts West Nile virus, does that person develop a natural immunity to future infection by the virus?
A. It is assumed that immunity will be lifelong; however, it may wane in later years.

Regarding incidence, roughly 20,000 cases have been reported in the US since 1999. Assuming that 80% of cases have mild or no symptoms, that translates to about 100,000 people infected, or 0.03% of the population. It’s a quite trivial disease on a population level.

With regard to the probabily of contracting the disease:

Q. If I live in an area where birds or mosquitoes with West Nile virus have been reported and a mosquito bites me, am I likely to get sick?
A. No. Even in areas where the virus is circulating, very few mosquitoes are infected with the virus. Even if the mosquito is infected, less than 1% of people who get bitten and become infected will get severely ill. The chances you will become severely ill from any one mosquito bite are extremely small.

[groman]

Not to hijack but I can’t wrap my head around the West Nile virus… What’s the big deal? Is the name catchy?

It seems a lot less deadly and a lot less virulent then even the relatively mild strains of influenza. The flu does not leave 80% of infected people without symptoms, and a lot of people who get the flu and survive (as in an influenza virus, not stomach flu or cold) wish they were dead. The west nile virus seems like a really mild version of the common cold that sometimes causes encaphilitis in the elderly - high prices and young people using curse words causes pneumonia in the elderly and we’re not freaking out about that are we?

[Colibri]

@groman

Not to hijack but I can’t wrap my head around the West Nile virus… What’s the big deal? Is the name catchy?

That, and that it’s novel. However, although pretty trivial itself, it does illustrate how easy it is these days for “emerging diseases” to spread globally.

[myrnajean]

@groman

Not to hijack but I can’t wrap my head around the West Nile virus… What’s the big deal? Is the name catchy?

It seems a lot less deadly and a lot less virulent then even the relatively mild strains of influenza. The flu does not leave 80% of infected people without symptoms, and a lot of people who get the flu and survive (as in an influenza virus, not stomach flu or cold) wish they were dead. The west nile virus seems like a really mild version of the common cold that sometimes causes encaphilitis in the elderly - high prices and young people using curse words causes pneumonia in the elderly and we’re not freaking out about that are we?

I’ve wondered about that too. The fatality rate is really quite low.

If the media did coverage about, say, lightening strikes, bathtub slips, or closing the garage door on the hood of your car, and they made a big deal everytime someone had an incident, it would seem like some kind of epidemic.

(oh my god!! look out! The garage door is coming!!!)