Sunday, 14 September 2008

How infectious is meningococcus?

This'll be the first of two posts - the following one will ask the same question of TB, and the contrast is actually fascinating.

But let's not prejudge the conclusion - we shall start with Neiserria meningitidis, affectionately known as meningococcus. The crucial question in determining it's infectivity is this: how does it spread?

Neiserria meningitiditis doesn't survive for long outside the human body, and nor does it have an animal vector to act as a storage vessel until it can get back into a human. Therefore it must go from one human more or less straight to the next. People are infected when they come into direct contact with the organism (usually from the nasal secretions of infected patients) or when they inhale respiratory droplets containing it. Both of these methods of contagion are vastly facilitated by viral upper respiratory infections, which frequently induce both nasal secretions and coughing.

So, what are the odds of getting it? The matter is of some importance, since Neiserria meningitidis is capable of producing a nasty meningitis (hence it's name!). Worried family members and health care workers need to know whether or not they should take antibiotic prophylaxis to try to prevent the same fate.

Here are the facts, courtesy of a fantastically interesting article from the New England Journal of Medicine, entitled "How contagious are Common Respiratory Tract Infections?" (N Engl J Med 2003;348:1256-66). Close family members of a person infected with meningococcus have anywhere between a 1:400 to a 1:50 risk of contagion, which is actually lower than most people think. Schoolmates and work colleagues are better off still - with only a 1:3000 to a 1:200 chance. And casual social contacts (those who might come into contact with the infected person infrequently for short periods of time) have no increased risk of getting the disease when compared with someone on the other side of the country.

These figures may surprise you, because there is often a good deal of panic when meningococcus is diagnosed. This is probably because of the meningitis that it causes. As these figures show, however, this risk is rather exaggerated. The author of the article states:

Despite the public fear, bordering on hysteria, that may follow a case of meningococcal disease, more than 95 percent of cases in the United States and other developed countries are sporadic. Thus, in the majority of instances, a second case does not follow a first one. This is why, when a single case occurs in a schoolchild, the Centers for Disease Control and Prevention recommends prophylactic treatment for family contacts but not schoolmates.

And health care workers? The best thing, as always, is hand washing. In the case of meningitis, unless the patient is coughing profusely (which is decidedly unlikely), it is only really upper respiratory tract secretions that are infectious. Nurses, for instance, are at a slightly increased risk of catching the disease, since they often directly exposed to secretions. On the other hand, doctors who spend only a few minutes per day by a particular patient's bedside are usually at no greater risk of infection than the population at large.


  1. The Meningitis Foundation of America (MFA), a national organization, would like the public and media to know that information is available regarding the diagnosis, treatment and prevention of meningitis. MFA was founded by parents whose children were affected by meningitis. In addition to supporting vaccines and other means of preventing meningitis, the MFA provides information to educate the public and medical professionals so that the early diagnosis, treatment and, most important, prevention of meningitis, will save lives. Meningitis is a dangerous and sometimes fatal inflammation of the brain and/or spinal cord that can leave survivors with serious life-long physical problems such as deafness, brain damage and other disabilities, meningitis can sometimes result in loss of limbs. MFA would like to be considered as a news resource for the disease. For further information, visit the MFA website at

    MFA is proud to announce the new C.I.S.S. Container Identification Scratch System
    When we participate in sporting events or mingle at social gatherings it is possible to lose track of our water bottles and/or beverage cans, especially those served in containers that are very similar or identical to a container from which you are drinking. This carries the risk of transmitting an illness, such as meningitis or the common cold or flu. The Container Identification Scratch System, or C.I.S.S., is a fun way to make sure you always know your drink from others. Use it at sporting events or at a family gatherings and reduce the waste from forgotten drinks. Simply scratch your number from the C.I.S.S. label and identify your drink. For more information please contact Bob Gold at and

    Thank you,

    Meningitis Foundation of America
    212 W 10th Street, Suite B-330
    Indianapolis, IN 46202
    (800) 668-1129

  2. MFA certainly looks like an interesting resource.

    I'm a bit skeptical about the purported effectiveness of the CISS, however. I wonder if the MFA (or anyone else) has done any actual research in this regard? I'd be interested to know.