A deadly strain of bacterial meningitis has been circulating among gay and bisexual men in New York City, infecting 22 men and killing seven since 2010.

The rate of infection for the invasive meningococcal disease appears to have accelerated in recent months, with four new cases reported this year. Three of the last five cases have been fatal, according to the New York City Department of Health and Mental Hygiene.

The recent rise in infections prompted public health officials to increase awareness of the outbreak and release vaccination guidelines.

Men most at risk for meningitis are those who regularly have intimate contact with other men at parties, bars, and clubs, as well as those who meet with other men through a website or app, such as Grindr.

About half of the men infected have been HIV positive. Because HIV infection compromises the immune system, HIV positive people are more likely to become infected by invasive meningococcal disease and also more likely to die from the infection.

Officials in New York recommend that any men who have intimate contact with other men who are either HIV-positive, or HIV-negative and non-monogamous be vaccinated. The recommendation extends to men who have intimate contact with men while visiting the city since September 2012.

Those unsure of whether they meet the above criteria should talk to their medical providers to see if the meningococcal vaccine is right for them.

The bacteria is not necessarily transmitted through sex. People typically carry the bacteria in the nose and mouth, and spread it through kissing, sharing drinks and utensils, or coughing in close face-to-face contact.

Meningitis is a medical emergency in which the membranes that surround the brain and spinal cord becomes inflamed. It can be caused by a number of microorganisms — bacterial, viral, or fungal. Common symptoms resemble the flu — high fever, headache, stiff neck, and rash — and may occur 2-10 days after infection.

Since the disease progresses quickly, people who suspect meningococcal infection and have these symptoms should seek medical treatment quickly. Treatment typically involves supportive care and common antibiotics, such as penicillin.

"Meningitis symptoms usually come on quickly, and the disease can be fatal if not treated right away," said Dr. Thomas Farley, health commissioner of New York City. "Vaccination is the best defense. I urge all men who meet these criteria - regardless of whether they identify as gay - to get vaccinated now and protect themselves from this disease before it is too late."

The vaccine is only a preventative measure and does not treat an existing infection. However, vaccinations also reduce the risk of being a carrier for the disease, protecting even those who have yet to be vaccinated.

In April, Brett Shaad, 33 year old West Hollywood lawyer died from bacterial meningitis, which generated fears that the outbreak spread to the west coast. However, officials from the U.S. Centers for Disease Control and Prevention (CDC) confirmed the strain that infected him was very different than that circulating in New York, and that his death was most likely unrelated.

Although there have been no confirmed cases since February 15, city public health officials remain cautious and urge the community to spread the word about the risk of meningitis and the importance of vaccination. The number of meningococcal vaccinations administered in the city has risen to 10,200 as of May 13, which shows that some public health efforts are taking hold in the community.

However, as indicated in a recent story published in The New York Times, many members of the gay and bisexual community of New York are still unaware that the meningitis outbreak even exists. The upcoming gay pride celebration in June, which draw in thousands from outside the city, is a worrisome opportunity to spread infection.

In addition to the aforementioned men, the CDC recommends that adolescents, college freshmen living in dormitories, and people travelling to countries where meningitis is common receive the vaccine. A booster shot is required every five years. The vaccine does not contain a live form of the bacteria, so there is no risk of contracting meningitis from being vaccinated. The vaccine carries a very low risk allergic response, like all vaccines.

The city of New York has released a list of free and confidential sexually-transmitted disease clinics that offer the meningococcal vaccine.